A waitress stands next to disinfectants after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

A Montenegrin Army soldier walks on a street after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Women wearing masks walk on a street after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

A women rides a bicycle next to people waiting for a bus after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

People enjoy warm weather at a caffe terrace after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

People sit at a cafe terrace after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

A women passes by the Independence Day posters after Prime Minister Dusko Markovic declared the country the coronavirus disease (COVID-19)-free in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Montenegro's Prime Minister Dusko Markovic is seen during an announcement that Montenegro is coronavirus-free country in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Montenegro's Prime Minister Dusko Markovic announces that Montenegro is coronavirus-free country in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Montenegro's Prime Minister Dusko Markovic announces that Montenegro is coronavirus-free country in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Montenegro's Prime Minister Dusko Markovic announcing that Montenegro is coronavirus-free country in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

Montenegro's Prime Minister Dusko Markovic announcing that Montenegro is coronavirus-free country in Podgorica, Montenegro, May 25, 2020. REUTERS/Stevo Vasiljevic

World number one tennis player Novak Djokovic poses after a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic leaves after a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic speaks at a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic reacts at a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic holds a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

World number one tennis player Novak Djokovic arrives to hold a news conference on the upcoming Adria Tour tennis tournament, in Belgrade, Serbia, May 25, 2020. REUTERS/Marko Djurica

Migrants swing at playground inside Principovac camp for migrants near Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Migrants cook chicken for dinner inside Principovac camp for migrants near Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Migrants play volleyball at Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Migrants play volleyball at Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A migrant takes a rest inside Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A migrant prays in a makeshift mosque inside Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Serbian army soldiers check migrant's documents near the Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Serbian army soldiers patrol near the Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A migrant prays in a makeshift mosque inside Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Migrants from Vietnam stand at playground inside Principovac camp for migrants near Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A migrant carries fire wood at Principovac camp for migrants near Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A migrant girl looks through a window inside Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Serbian army soldiers stand guard along the fence of Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

Serbian army soldiers stand guard along the fence of Sid-Point camp for migrants in Sid, Serbia, May 21, 2020. Picture taken May 21, 2020. REUTERS/Marko Djurica

A woman waits for a bus amid the coronavirus disease (COVID-19) outbreak in Belgrade, Serbia, May 19, 2020. REUTERS/Marko Djurica

A boy rides a scooter in an underpass amid the coronavirus disease (COVID-19) outbreak in Belgrade, Serbia, May 19, 2020. REUTERS/Marko Djurica

A woman works in a fast food street kiosk amid the coronavirus disease (COVID-19) outbreak in Belgrade, Serbia, May 19, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic speaks during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban gestures during a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban speaks during a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban attends a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic and Hungarian Prime Minister Viktor Orban leave after a news conference at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic reacts during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic reacts during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic speaks during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban speaks during a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic speaks during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban reacts during a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban speaks during a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic speaks during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic speaks during a news conference with Hungarian Prime Minister Viktor Orban at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic and Hungarian Prime Minister Viktor Orban attend a news conference at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Hungarian Prime Minister Viktor Orban attends a news conference with Serbian President Aleksandar Vucic at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Serbian President Aleksandar Vucic and Hungarian Prime Minister Viktor Orban arrive to attend a news conference at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Members of the media wearing protective face masks wait for Serbian President Aleksandar Vucic and Hungarian Prime Minister Viktor Orban to attend a news conference at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica

Members of the media wearing protective face masks wait for Serbian President Aleksandar Vucic and Hungarian Prime Minister Viktor Orban to attend a news conference at the presidential building in Belgrade, following the coronavirus disease (COVID-19) outbreak, in Serbia, May 15, 2020. REUTERS/Marko Djurica