In this Friday, February 27, 2015 photo, an Israeli high-school senior preparing to join the Israeli military later this year participates in a privately run training camp for military combat fitness near Yakum, central Israel. With a mandatory three-year military service looming after graduation, teenage boys, and increasingly girls too, are gearing up for the draft, getting into shape and trying to improve their chances of acceptance into elite combat units. (Photo by Oded Balilty/AP Photo)

Students in Aone’s elementary school during break in between the class on April 9, 2015. The school has only six students, two of whom are from the same family. Similarly small schools can be found throughout Japan. (Photo by Ko Sasaki/The Washington Post)

Francisco da Silva Vale, 61, cools off fish with ice produced on solar-powered ice machines at Vila Nova do Amana community in the Sustainable Development Reserve, in Amazonas state, Brazil, September 23, 2015. Three solar-powered machines, are producing about ninety kilos of ice per day, in a region with poor access to electric energy, which used to be produced only with diesel oil, in the Amazon rain forest. (Photo by Bruno Kelly/Reuters)

Men look on from the banks of Rio Doce (Doce River), which was flooded with mud after a dam owned by Vale SA and BHP Billiton Ltd burst, as the river joins the sea on the coast of Espirito Santo in Regencia Village, Brazil, November 22, 2015. (Photo by Ricardo Moraes/Reuters)

Vladimir Putin looks at a model of the Tupolev TU-160 bomber, or Blackjack, that was presented to him on his arrival in Olenegorsk, Russia, August 16, 2005. Putin flew in the Tupolev TU-160 bomber and took part in the launch of cruise missiles in the Arctic north. (Photo by Reuters/ITAR-TASS/Presidential Press Service)

Blue, white and red brassieres, the colours of the French national flag, hang from a balcony in Marseille, France, November 27, 2015 as the French President called on all French citizens to hang the tricolour national flag from their windows on Friday to pay tribute to the victims of the Paris attacks during a national day of homage. (Photo by Jean-Paul Pelissier/Reuters)

Participants run through the streets of the Back Bay during the 16th annual Santa Speedo Run in Boston, Massachusetts, December 12, 2015. (Photo by Brian Snyder/Reuters)

Labourers load a three-wheeled vehicle onto the back of a van at the Mercato market in Addis Ababa October 9, 2015. Addis Ababa's “Mercato” – Italian for “market” – is reputedly the biggest open-air market in Africa, lying in the west of the capital. (Photo by Tiksa Negeri/Reuters)