Women pose for a picture at Havana city, Cuba, March 17, 2016. Obama arrives in Havana on Sunday for a historic visit that seals a rapprochement he and Cuban President Raul Castro agreed in December 2014 after 18 months of secret negotiations. (Photo by Ivan Alvarado/Reuters)

In this photograph taken on February 18, 2016, Pakistani children ride on swings in the predominantly Pashtun Korangi District of Karachi. In a rundown district of Karachi, Rabia balks at a neighbour's proposal to vaccinate her children, demonstrating one of the biggest hurdles to eradicating polio in Pakistan by the end of the year: confused and frightened parents. (Photo by Asif Hassan/AFP Photo)

A girl stretches next to a pram on the embankment of the Moskva river in Moscow on October 18, 2018. The European part of Russia enjoys an unusually warm weather for the season with temperatures reaching up to 22 degrees centigrade. (Photo by Mladen Antonov/AFP Photo)

A man walks his dog as the sun sets in a park in Frankfurt, Germany, Monday, September 18, 2017. Cool damp weather is set to continue in this part of Germany for the next few days with temperatures in the mid teens Celsius. (Photo by Michael Probst/AP Photo)

Children play in an outdoor shower as a soldier takes part in a surprise operation in the Manguinhos slum in Rio de Janeiro, Brazil, Thursday, January 18, 2018. Troops have been sent to Rio due to the increase of the violence, and in an attempt to help restore order, but so far have had little impact. The operation on Thursday took place three weeks ahead of Carnival, when thousands of tourists are expected to arrive in the city. (Photo by Leo Correa/AP Photo)

People visit the autonomous urban concept car Renault EZ-GO during the first press day of the Geneva International Motor Show on March 6, 2018 in Geneva. The show opens to the public on March 8 and runs through March 18. (Photo by Fabrice Coffrini/AFP Photo)

“Left behind” children Luo Hongni, 11 (L) and brother Luo Gan,10, carry flowers to be used as feed while doing chores in the fields on December 18, 2016 in Anshun, China. Like millions of Chinese children, the four Luo siblings are being raised by their grandparents in rural China as their parents left to find work in urban areas. (Photo by Kevin Frayer/Getty Images)

A young reveller participates in the annual Trinidad and Tobago Red Cross Society's Children's Carnival Competition at the Queen's Park Savannah in Port-Of-Spain, Trinidad and Tobago February 18, 2017. (Photo by Andrea De Silva/Reuters)