Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Christmas service at the Cathedral of Christ the Saviour in Moscow, Russia January 7, 2020. REUTERS/Evgenia Novozhenina

Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Christmas service at the Cathedral of Christ the Saviour in Moscow, Russia January 7, 2020. REUTERS/Evgenia Novozhenina

Russia's President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Cathedral of Christ the Saviour in Moscow, Russia April 28, 2019. REUTERS/Evgenia Novozhenina TPX IMAGES OF THE DAY

Russia's Prime Minister Dmitry Medvedev, his wife Svetlana, President Vladimir Putin and Moscow's Mayor Sergei Sobyanin attend the Orthodox Easter service at the Cathedral of Christ the Saviour in Moscow, Russia April 27, 2019. REUTERS/Evgenia Novozhenina

Russia's President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana smile as they attend the Orthodox Easter service at the Cathedral of Christ the Saviour in Moscow, Russia April 28, 2019. REUTERS/Evgenia Novozhenina

Russia's President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Cathedral of Christ the Saviour in Moscow, Russia April 28, 2019. REUTERS/Evgenia Novozhenina

Russia's President Vladimir Putin, Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Cathedral of Christ the Saviour in Moscow, Russia April 27, 2019. REUTERS/Evgenia Novozhenina

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia April 8, 2018. Alexander Zemlianichenko/Pool via REUTERS TPX IMAGES OF THE DAY

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev, his wife Svetlana and Moscow Mayor Sergei Sobyanin attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia April 8, 2018. Alexander Zemlianichenko/Pool via REUTERS

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev, his wife Svetlana and Moscow Mayor Sergei Sobyanin attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia April 8, 2018. Alexander Zemlianichenko/Pool via REUTERS

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia April 8, 2018. Alexander Zemlianichenko/Pool via REUTERS

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia April 8, 2018. Alexander Zemlianichenko/Pool via REUTERS

Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 7, 2018. REUTERS/Maxim Shemetov

Russian Prime Minister Dmitry Medvedev and his wife Svetlana pray during a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 7, 2018. REUTERS/Maxim Shemetov

Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 7, 2018. REUTERS/Maxim Shemetov

Russian Prime Minister Dmitry Medvedev and his wife Svetlana pray during a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 6, 2018. REUTERS/Maxim Shemetov

Russian President Vladimir Putin, Moscow Mayor Sergei Sobyanin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, early April 16, 2017. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin, Moscow Mayor Sergei Sobyanin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, early April 16, 2017. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, early April 16, 2017. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, early April 16, 2017. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, early April 16, 2017. REUTERS/Sergei Karpukhin

Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 6, 2017. REUTERS/Sergei Karpukhin

Russian Prime Minister Dmitry Medvedev and his wife Svetlana attend a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 6, 2017. REUTERS/Sergei Karpukhin

Russian Prime Minister Dmitry Medvedev and his wife Svetlana pray during a service on Orthodox Christmas at the Christ the Saviour Cathedral in Moscow, Russia January 6, 2017. REUTERS/Sergei Karpukhin

Svetlana Medvedeva, wife of Russian Prime Minister Dmitry Medvedev, attends the blessing ceremony of the new Holy Trinity Russian Orthodox Cathedral in Paris, France, December 4, 2016. REUTERS/Benoit Tessier

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev and his wife Svetlana attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin (2nd R), Moscow Mayor Sergei Sobyanin (R), Prime Minister Dmitry Medvedev and his wife Svetlana attend an Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev and his wife Svetlana, attend an Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev and his wife Svetlana, pray during an Orthodox Easter service at the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev and his wife Svetlana, attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev and his wife Svetlana attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, Russia, May 1, 2016. REUTERS/Sergei Karpukhin

Russia's President Vladimir Putin (R, front) receives a gift from Patriarch of Moscow and All Russia Kirill as Prime Minister Dmitry Medvedev (2nd R, back) and his wife Svetlana standing nearby during the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow April 11, 2015. Picture taken April 11, 2015. REUTERS/Alexander Zemlianichenko/Pool

Russia's President Vladimir Putin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana attend the Orthodox Easter service at the Christ the Saviour Cathedral in Moscow April 11, 2015. Picture taken April 11, 2015. REUTERS/Alexander Zemlianichenko/Pool TPX IMAGES OF THE DAY

Russian President Vladimir Putin (2nd R), Moscow Mayor Sergei Sobyanin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana pray during an Orthodox Easter service at the Christ the Saviour Cathedral in Moscow April 12, 2015. REUTERS/Alexander Zemlianichenko/Pool

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) smile during an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 20, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin (2nd R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana (2nd L), Moscow Mayor Sergei Sobyanin attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 20, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin talks to Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) during an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin talks to Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) during an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow, April 19, 2014. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian Prime Minister Dmitry Medvedev (L) and his wife Svetlana Medvedeva (C), attend the opening ceremony of the 2014 Paralympic Winter Games in Sochi, March 7, 2014. REUTERS/Alexander Demianchuk (RUSSIA - Tags: OLYMPICS SPORT POLITICS)

Russian President Vladimir Putin, Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service conducted by the Patriarch of Moscow and All Russia Kirill in the Christ the Saviour Cathedral in Moscow May 5, 2013. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION ANNIVERSARY POLITICS)

Russian President Vladimir Putin (C) kisses Kirill, Patriarch of Moscow and All Russia, as Svetlana Medvedeva (R), wife of Prime Minister Dmitry Medvedev, looks on during an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow May 5, 2013. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION ANNIVERSARY POLITICS)

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana (obscured) attend an Orthodox Easter service conducted by the Patriarch of Moscow and All Russia Kirill in the Christ the Saviour Cathedral in Moscow May 5, 2013. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION ANNIVERSARY POLITICS)

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service conducted by the Patriarch of Moscow and All Russia Kirill in the Christ the Saviour Cathedral in Moscow May 5, 2013. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION ANNIVERSARY POLITICS TPX IMAGES OF THE DAY)

Russian President Vladimir Putin (R), Prime Minister Dmitry Medvedev (L) and his wife Svetlana (C) attend an Orthodox Easter service conducted by the Patriarch of Moscow and All Russia Kirill in the Christ the Saviour Cathedral in Moscow May 5, 2013. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION ANNIVERSARY POLITICS)

Lyudmila (R), wife of Russia's new President Vladimir Putin, and Svetlana, wife of former President Dmitry Medvedev, speak in Cathedral Square at the Kremlin in Moscow, May 7, 2012. Vladimir Putin took the oath as Russia's president on Monday with a ringing appeal for unity at the start of a six-year term in which he faces growing dissent, economic problems and bitter political rivalries. REUTERS/Alexander Zemlianichenko/Pool (RUSSIA - Tags: POLITICS)

Former Russian President Dmitry Medvedev (L) and his wife Svetlana leave after attending a ceremony to inaugurate Vladimir Putin as new president in Cathedral Square at the Kremlin in Moscow, May 7, 2012. Vladimir Putin took the oath as Russia's president on Monday with a ringing appeal for unity at the start of a six-year term in which he faces growing dissent, economic problems and bitter political rivalries. REUTERS/Alexander Zemlianichenko/Pool (RUSSIA - Tags: POLITICS)

Russia's new President Vladimir Putin (R) kisses his wife Lyudmila, while former President Dmitry Medvedev (L) kisses his wife Svetlana, during an inauguration ceremony in Cathedral Square at the Kremlin in Moscow May 7, 2012. Putin appealed for unity in Russia after being sworn as president on Monday and pledged to strengthen democracy in his new six-year term. REUTERS/Alexander Zemlianichenko/Pool (RUSSIA - Tags: POLITICS)

Russian President Dmitry Medvedev (L), first lady Svetlana (C) , and Prime Minister and President-elect Vladimir Putin attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow April 14, 2012. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Dmitry Medvedev (L), first lady Svetlana (2nd L), Prime Minister and President-elect Vladimir Putin and Moscow Mayor Sergei Sobyanin (R) attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow April 14, 2012. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Dmitry Medvedev (L), first lady Svetlana (C) , and Prime Minister and President-elect Vladimir Putin attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow April 14, 2012. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Dmitry Medvedev (L),and first lady Svetlana attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow April 14, 2012. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Dmitry Medvedev (L), first lady Svetlana (C) , and Prime Minister and President-elect Vladimir Putin attend an Orthodox Easter service in the Christ the Saviour Cathedral in Moscow April 14, 2012. REUTERS/Maxim Shemetov (RUSSIA - Tags: RELIGION POLITICS)

Russian President Dmitry Medvedev (L) looks at his ballot paper as he stands with his wife Svetlana before they cast their votes in a polling station in Moscow March 4, 2012. Prime Minister Vladimir Putin is almost certain to win a third presidential term in an election that began on Sunday in Russia's far east, though opponents have challenged the legitimacy of a vote they say is skewed in his favour. REUTERS/Kirill Kudryavtsev/Pool (RUSSIA - Tags: ELECTIONS POLITICS)

Russian President Dmitry Medvedev (L) stands with his wife Svetlana as she casts her vote in a polling station in Moscow March 4, 2012. Prime Minister Vladimir Putin is almost certain to win a third presidential term in an election that began on Sunday in Russia's far east, though opponents have challenged the legitimacy of a vote they say is skewed in his favour. REUTERS/Kirill Kudryavtsev/Pool (RUSSIA - Tags: ELECTIONS POLITICS)

Russian President Dmitry Medvedev (L) stands with his wife Svetlana as she casts her vote in a polling station in Moscow March 4, 2012. Prime Minister Vladimir Putin is almost certain to win a third presidential term in an election that began on Sunday in Russia's far east, though opponents have challenged the legitimacy of a vote they say is skewed in his favour. REUTERS/Kirill Kudryavtsev/Pool (RUSSIA - Tags: ELECTIONS POLITICS)

Russian President Dmitry Medvedev (L) stands with his wife Svetlana as she casts her vote in a polling station in Moscow March 4, 2012. Prime Minister Vladimir Putin is almost certain to win a third presidential term in an election that began on Sunday in Russia's far east, though opponents have challenged the legitimacy of a vote they say is skewed in his favour. REUTERS/Kirill Kudryavtsev/Pool (RUSSIA - Tags: ELECTIONS POLITICS)