A combination of three photographs shows the U.S. flag atop the White House flying at half staff Sunday morning August 26 in honor of the death of Senator John McCain (top), back at full staff less than 24 hours later on Monday morning August 27 (middle) and then back down to half-staff Monday afternoon (bottom) in Washington, U.S., August 27, 2018. REUTERS/Joshua Roberts, Kevin Lamarque and Leah Millis 

A combination of three photographs shows the U.S. flag atop the White House flying at half staff Sunday morning August 26 in honor of the death of Senator John McCain (top), back at full staff less than 24 hours later on Monday morning August 27 (middle) and then back down to half-staff Monday afternoon (bottom) in Washington, U.S., August 27, 2018. REUTERS/Joshua Roberts, Kevin Lamarque and Leah Millis 

A combination of two photographs shows the U.S. flag atop the White House flying at half staff Sunday morning August 26 in honor of the death of Senator John McCain (top), but back at full staff less than 24 hours later on Monday morning (bottom) in Washington, U.S., August 27, 2018. REUTERS/Joshua Roberts and Kevin Lamarque 

A combination photo shows the lunar eclipse from a blood moon (top L) back to full moon (bottom right) in the sky over Frankfurt, Germany, July 27, 2018. REUTERS/Kai Pfaffenbach 

A combination photo shows the end of the full lunar eclipse near the western German city of Bonn, Germany, July 27 and 28, 2018. REUTERS/Wolfgang Rattay 

A combo picture shows artistic cappuccinos, realized by a teacher of the Mixology Academy Bartendering School during a lesson, in Rome, Italy July 20, 2018. REUTERS/Tony Gentile 

A combination of pictures shows (from top L to bottom R) participants using lances to push each other from their boats during the traditional Schifferstechen event, celebrated by the boatmen's guild similar to medieval jousting, on the river Limmat in Zurich, Switzerland July 7, 2018. REUTERS/Arnd Wiegmann 

FILE PHOTOS: Republican presidential nominee Donald Trump (L) holds a rally with supporters in Council Bluffs, Iowa, September 28, 2016 and Chinese President Xi Jinping waits for leaders to arrive at a summit in Shanghai May 21, 2014. REUTERS/Jonathan Ernst/Aly Song/File Photos 

A combo shows people posing with a canisters with gasoline after filling it at a gas station in the outskirts of Brasilia, Brazil May 29, 2018. (Top L-R) Vieira bought gasoline to take her pregnant sister to the hospital, Henrique bought gasoline for his father who needed to go to hospital, Moraes bought gasoline for his family's car. (Center L-R) Francisco bought gasoline for his private motorcycle, Machado bought gasoline to drive to the hospital and get medicine, Dos Santos bought gasoline for her private car. (Bottom L-R) Miranda bought gasoline for a sick friend, Silva bought gasoline for his father's car and Rodrigues bought gasoline for a sick elderly woman. REUTERS/Ueslei Marcelino 

FILE PHOTO: A combination photo shows Adult film actress Stephanie Clifford, also known as Stormy Daniels speaking in New York City, and U.S. President Donald Trump speaking in Washington, Michigan, U.S. on April 16, 2018 and April 28, 2018 respectively. . REUTERS/Brendan Mcdermid (L) REUTERS/Joshua Roberts (R)/File Photos 

A combination of pictures shows the Boeoegg, a snowman made of wadding and filled with firecrackers, burning in a bonfire in the Sechselaeuten square in Zurich, Switzerland, April 16, 2018. REUTERS/Arnd Wiegmann 

A combination of photgraphs shows blossoms in a public garden in Vienna, Austria, April 12, 2018. REUTERS/Heinz-Peter Bader 

A combination of file photos shows candidates (from L to R) Leftist front-runner Andres Manuel Lopez Obrador of the National Regeneration Movement (MORENA), Institutional Revolutionary Party (PRI) presidential candidate Jose Antonio Meade, presidential candidate for the National Action Party (PAN), leading a left-right coalition Ricardo Anaya, and Independent presidential candidate Margarita Zavala. REUTERS/Henry Romero/Ginnette Riquelme/Files Photos 

A combination picture shows candidates (L to R) Leftist front-runner Andres Manuel Lopez Obrador of the National Regeneration Movement (MORENA), Institutional Revolutionary Party (PRI) presidential candidate Jose Antonio Meade and presidential candidate for the National Action Party (PAN), leading a left-right coalition Ricardo Anaya, addressing the audience during a conference organised by the Mexican Construction Industry Association in Guadalajara, Mexico, March 23, 2018. Pictures taken on March 23, 2018. REUTERS/Henry Romero and Independent presidential candidate Margarita Zavala addresses supporters during a campaign kick-off for the July 1 presidential election at the Angel of Independence monument in Mexico City, Mexico March 30, 2018. Picture taken on March 30. REUTERS/Ginnette Riquelme 

A combination photo shows the "Puente Nuevo" (New Bridge) in the daytime (top), at night (C) and during Earth Hour in Ronda, near Malaga, Spain, March 24, 2018. REUTERS/Jon Nazca 

A combination photo shows the "Puente Nuevo" (New Bridge) at night (top) and during Earth Hour in Ronda, near Malaga, southern Spain, March 24, 2018. REUTERS/Jon Nazca 

A combination picture shows a view of the ancient Colosseum before and after the lights were switched off for Earth Hour in Rome, Italy, March 24, 2018. REUTERS/Stefano Rellandini 

A combination picture shows a view of the ancient Parthenon temple atop the Acropolis hill before (top) and during Earth Hour in Athens, Greece, March 24, 2018. REUTERS/Alkis Konstantinidis 

A combination photo shows the Stupa of Enlightenment, a holy monument constructed of granite, at the Buddhist Centre, before (bottom) and after the lights were switched off for Earth Hour, in Krasnoyarsk, Russia March 24, 2018. REUTERS/Ilya Naymushin 

A combination of six pictures showing figures on the top of a stick used by believers during the "Endiablada" festival in Almonacid del Marquesado, Spain February 2, 2018. REUTERS/Sergio Perez 

A combination picture shows a cardboard grenade hanging inside a military vehicle at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and electricity wires over a busy street in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows an exit door where released detainees are turned over to the countries that have agreed to accept them at the Guantanamo Bay U.S. Naval Base, Cuba, June 3, 2017 (L) and a woman riding a train in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows books inside a sample cell displayed within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and food displayed on shelves at a market in the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows magazines at a coffee shop at the U.S. Naval Base in Guantanamo Bay, Cuba, June 2, 2017 (L) and a man sitting outside a house waiting to join a parade during a local holiday in the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows a fence at the U.S. Naval Base in Guantanamo Bay, Cuba, June 2, 2017 (L) and a window of a house in the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows an entrance to a bunker at the U.S. Naval Base in Guantanamo Bay, Cuba, June 2, 2017 (L) and a house door in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows an unidentified member of the U.S. Army standing by an empty cell inside a prison at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and a girl taking a break during a soccer game under heavy rain in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows clocks showing time in different capitals of the world at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and globes and books inside a local school in the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows public telephones outside a shopping mall at the U.S. Naval Base in Guantanamo Bay, Cuba, June 2, 2017 (L) and empty tables and chairs inside a children's play area in the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows a buoy near the U.S. Naval Base in Guantanamo Bay, Cuba, June 2, 2017 (L) and a sugar cane field near the city of Guantanamo, Cuba, December 7, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows a table at a restaurant used by U.S. military personnel at the Guantanamo Bay U.S. Naval Base, Cuba, June 3, 2017 (L) and local residents waiting in line to buy bread in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows an unidentified member of the U.S. Army standing by an empty cell inside a prison at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and a girl standing by a fast food restaurant in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

A combination picture shows an unidentified detainee walking along a cellblock of a prison at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and people riding a bus in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. TPX IMAGES OF THE DAY 

A combination picture shows soccer balls inside a cellblock at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and a boy running with a ball during a soccer game in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. TPX IMAGES OF THE DAY 

A combination picture shows a sample cell within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and local residents playing dominoes outside their homes in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. TPX IMAGES OF THE DAY 

A combination picture shows a road near a prison at the U.S. Naval Base in Guantanamo Bay, Cuba, June 3, 2017 (L) and a boy walking along train rails in the outskirts of the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Local residents ride on a bus in the city of Guantanamo, Cuba, December 6, 2017. REUTERS/Carlos Barria SEARCH "GUANTANAMO COMBO" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. TPX IMAGES OF THE DAY 

A combination picture shows models who attend a rehearsal (Top) and later as they present creations by French designer Christophe Josse as part of his Haute Couture Spring-Summer 2018 fashion show in Paris, France, January 25, 2018. REUTERS/Charles Platiau 

A combination picture shows Paris' Notre Dame Cathedral with people walking along the Seine River on August 28, 2017 (Top) and with its banks covered by muddy waters from current flooding after continued rainfall in the country, in Paris, France, January 25, 2018. Top picture taken August 28, 2017. REUTERS/Philippe Wojazer 

A combination picture shows the logos of some of the companies taking part in the "Salon International de la Haute Horlogerie" (SIHH) watch fair: Montblanc, Cartier, Jaeger-LeCoultre, A. Lange & Soehne, Van Cleef & Arpels, Vacheron Constantin, Roger Dubuis, Girard-Perregaux, Ulysse Nardin, Piaget, IWC and Parmigiani Fleurier, in Geneva, Switzerland, January 15, 2018. Pictures taken January 15, 2018. REUTERS/Denis Balibouse 

A combination picture shows (L) conjoined twins Haneen and Farah in an incubator at a hospital in Gaza City on October 26, 2017; and (R) Haneen lying on a bed after she was separated from her sister Farah at King Abdullah Specialist Children hospital in Riyadh, Saudi Arabia on January 9, 2018. REUTERS/Mohammed Salem (L) & Faisal Al Nasser (R) 

A combination picture shows a baby caressing Pope Francis during his Wednesday general audience in Paul VI hall at the Vatican January 3, 2018. REUTERS/Remo Casilli TPX IMAGES OF THE DAY 

A combination picture shows golfers Hiromi Kobayashi of Japan (L) and Shin Ji-yai of South Korea (R) at Wykagyl Country Club in New Rochelle, New York, U.S., July 16, 1998 and at Torrey Pines Golf Course in San Diego, California, U.S., September 20, 2009 in these file photos respectively. REUTERS/Jeff Christensen, Mike Blake/File Photo 

A combination picture shows a demonstrator dressed as Santa Claus before and after he gets wounded during clashes with Israeli troops, at a protest as Palestinians call for a "Day of Rage" in response to U.S. President Donald Trump's recognition of Jerusalem as Israel's capital, near the border with Israel in the southern Gaza Strip, December 22, 2017. REUTERS/Ibraheem Abu Mustafa 

A combination picture shows a Palestinian man falling down after being shot by Israeli border policemen near the Jewish settlement of Beit El, near the West Bank city of Ramallah December 15, 2017 REUTERS/Goran Tomasevic 

A combination photo shows Democratic Alabama U.S. Senate candidate Doug Jones (L) and Republican U.S. Senate candidate Roy Moore (R) at their respective election night parties in Birmingham and Montgomery, Alabama, U.S., December 12, 2017. REUTERS/Marvin Gentry/Jonathan Bachman 

A combination picture shows women who have tattoos in Alakus and Dikmen villages near Kiziltepe, a town in southeastern province of Mardin and in Kisas village near southeastern province of Sanliurfa, from pictures taken November 20, 21 and 22, 2017. Top row L-R: Ayse Yusufoglu (84), Senem Dogru (80), Hedle Ertas (84); bottom row L-R: Duri Yusufoglu (75), Hulu Aydogdu (87), Fatma Dogru (70) REUTERS/Umit Bektas 

A combination picture shows women who have tattoos on their faces in Alakus and Dikmen villages near Kiziltepe, a town in southeastern province of Mardin and in Kisas village near southeastern province of Sanliurfa, from pictures taken November 20, 21 and 22, 2017. Top row L-R: Ayse Yusufoglu (84), Senem Dogru (80), Fatma Dogru (70); bottom row L-R: Azize Turan (75), Hatice Demircan (80), Duri Yusufoglu (82). REUTERS/Umit Bektas 

A combination picture shows markings and signs along boats and locks along the Ohio River, U.S., between September 15, 2017 and September 18, 2017. REUTERS/Brian Snyder SEARCH "SNYDER BARGES" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Trampoline Gymnastics - 32nd FIG Trampoline Gymnastics World Championships 2017 - Men's Trampoline Final - Sofia, Bulgaria - November 12, 2017. A combination picture shows Uladzislau Hancharou of Belarus, Dong Dong of China, Allan Morante of France, Aleh Rabtsau of Belarus, Lei Gao of China and Dmitrii Ushakov of Russia as they compete. REUTERS/Stoyan Nenov 

A combination picture shows a slogan that reads "No Future in Fossil Fuels", projected in nine different languages, by activists of the environmental organisation Greenpeace, on the cooling tower of RWE coal power plant, one of Europe's biggest electricity companies in Neurath, north-west of Cologne, Germany, November 10, 2017. Combination picture of nine images shows following languages (L-R) top row: Fijian, English, German, middle row: French, Chinese, Dutch and bottom row: Polish, Spanish and Italian. REUTERS/Wolfgang Rattay TPX IMAGES OF THE DAY 

A combination picture shows a slogan that reads "No Future in Fossil Fuels", projected in nine different languages, by activists of the environmental organisation Greenpeace, on the cooling tower of RWE coal power plant, one of Europe's biggest electricity companies in Neurath, north-west of Cologne, Germany, November 10, 2017. Combination picture of nine images shows following languages (L-R) top row: Fijian, English, German, middle row: French, Chinese, Dutch and bottom row: Polish, Spanish and Italian. REUTERS/Wolfgang Rattay 

A combination picture shows Chilean presidential candidates during a live televised debate, (top row, L to R) Carolina Goic from Christian Democracy Party, Jose Antonio Kast from far-right, Sebastian Pinera from "Chile Vamos" (Let's Go Chile) coalition, Alejandro Guillier from government coalition, (Bottom row, L to R) Beatriz Sanchez from "Frente Amplio" (Wide Front) coalition, Marco Henriquez-Ominami from Progressive Party, Eduardo Artes from Union Patriotic Party and Alejandro Navarro from "Pais" (Country) Party, in Santiago, Chile November 6, 2017. REUTERS/Ivan Alvarado 

A combination picture shows the cruiser Aurora, which fired the shot that announced the start of Russia's 1917 Bolshevik Revolution, during a light show dedicated to revolution's centenary in St. Petersburg, Russia November 4, 2017. REUTERS/Anton Vaganov TPX IMAGES OF THE DAY 

A combination picture shows the cruiser Aurora, which fired the shot that announced the start of Russia's 1917 Bolshevik Revolution, during a light show dedicated to revolution's centenary in St. Petersburg, Russia November 4, 2017. REUTERS/Anton Vaganov 

A combination picture shows leader of the Christian Democratic Union of Germany (CDU) Angela Merkel attending the weekly cabinet meeting at the Chancellery in Berlin, Germany, October 18, 2017. REUTERS/Hannibal Hanschke 

A combination picture shows Estelada (Catalan separatist flag), banners that read "Yes", and Spanish flags hanging from balconies in Barcelona, Spain, October 14, 2017. REUTERS/Gonzalo Fuentes 

A combination picture shows an opposition politician of the National Super Alliance (NASA) coalition, reacting after a gas canister fired by police hits his car during a protest along a street in Nairobi, Kenya October 13, 2017. REUTERS/Baz Ratner 

A combination picture shows wreaths being placed at affected areas of Mexico city after an earthquake in Mexico October 2, 2017. REUTERS/Nacho Doce 

Chilean presidential candidates are seen in a combination picture during a live televised debate, (top row, L to R) Eduardo Artes from Union Patriotic Party, Beatriz Sanchez from "Frente Amplio" (Wide Front) coalition, Jose Antonio Kast from far-right and Sebastian Pinera from "Chile Vamos" (Let's Go Chile) coalition, (Bottom row, L to R) Alejandro Guillier from government coalition, Marco Henriquez-Ominami from Progressive Party, Alejandro Navarro from "Pais" (Country) Party and Carolina Goic from Christian Democracy Party, in Valparaiso, Chile September 28, 2017. REUTERS/Rodrigo Garrido