Young gymnasts practice pull-up on a bar at a gymnasium of a sports school in Jiaxing, Zhejiang province April 11, 2015. (Photo by William Hong/Reuters)

Green algae sits on a beach in Kuwait City, Kuwait, 28 February 2017. The formation of green algae is a normal phenomenon that occurs every year at the shores of Kuwait. (Photo by Raed Qutena/EPA)

The Boeoegg, a giant symbolic snowman made of wadding and and filled with firecrackers burns on top of a bonfire in Sechselaeuten square on April 24, 2017 in Zurich. When the bells of the Saint Peter's church chime six o'clock, the bonfire under the snowman is set in fire and the guildsmen wearing historical costumes ride around the bonfire. The faster the head of the snowman explods the warmer and more beautiful the summer will be. (Photo by Michael Buholzer/AFP Photo)

A ballet dancer attends a photo shooting as activists from the environmentalist group Greenpeace unfurl a giant banner on the Eiffel Tower which reads “Liberty, Equality, Fraternity” in a call on French citizens to vote against the National Front (FN) presidential candidate Marine Le Pen, in Paris, France May 5, 2017. (Photo by Gonzalo Fuentes/Reuters)

Italian Air Force's aerobatic demonstration team, the Frecce Tricolori leave colourful vapour trails as they fly over the Altare della Patria monument on Republic Day (Festa della Repubblica) in Rome, Italy, 02 Jun 2017. The anniversary marks the founding of the Italian Republic in 1946. (Photo by Massimo Percossi/EPA)

Demonstrators perform a dance in front of riot policemen during a march called by students to request changes in the education system in Santiago, Chile September 5, 2017. (Photo by Ivan Alvarado/Reuters)

In this Thursday, October 5, 2017 photo, Chile's singer-songwriter Mon Laferte performs in concert at the Auditorio Nacional in Mexico City. The 34-year-old artist, who just received five Latin Grammy nominations, performed three sold-out concerts at the National Auditorium, on consecutive evenings, beginning Thursday. (Photo by Eduardo Verdugo/AP Photo)

A person poses on the track during a fashion competition at the Durban July horse racing event in Durban, South Africa, July 2, 2016. (Photo by Rogan Ward/Reuters)