Visitors look at graffiti art created by Brazilian artist Image during the 3rd annual Graffiti Fine Art Biennial International exhibit, at the Pavilion of Brazilian Cultures, in Sao Paulo, Brazil, Tuesday, April 21, 2015. The month-long event features the work of more than 60 street artists, representing 11 countries. (Photo by Andre Penner/AP Photo)

A white Bengal tiger cub plays with its mother in a zoo in the Siberian city of Novosibirsk, about 2,800 kilometers (1,750 miles) east of Moscow, Russia, Tuesday, April 21, 2015. Two blue-eyed Bengal tiger cubs were born in March to a couple of white tigers at Novosibirsk zoo. (Photo by Ilnar Salakhiev/AP Photo)

Members of the Barrio 18 gang run upon their arrival to the San Francisco Gotera penitentiary April 21, 2015. The Salvadoran goverment transfered 1,177 inmates, members of the Barrio 18 gang from Izalco jail to San Francisco Gotera in a effort to curb gang violence activity, according to local media. (Photo by Jose Cabezas/Reuters)

An airplane house is pictured in the village of Miziara, northern Lebanon May 12, 2015. Miziara prides itself on building residential homes that resemble ancient Greek temples and Egyptian ruins, one is even built in the shape of an Airbus A380. (Photo by Aziz Taher/Reuters)

Masked penitents holds their crosses during spring “Romeria Cruceros de Arce”, in Roncesvalles, northern Spain, Sunday, May 10, 2015. Every year on the second Sunday in spring, people with crosses march from their small Pyrenees towns to Roncesvalles Church in tribute of the Virgin. (Photo by Alvaro Barrientos/AP Photo)

A woman reacts as she uses a selfie stick to take a photo of herself at Tiananmen Square in Beijing, China, Thursday, April 30, 2015. Selfie sticks are gaining popular in China, and many people are using them at popular tourist destinations. (Photo by Andy Wong/AP Photo)

Model Karlie Kloss walks on the red carpet as she arrives for the opening ceremony and the screening of the film “La tete haute” out of competition during the 68th Cannes Film Festival in Cannes, southern France, May 13, 2015. (Photo by Benoit Tessier/Reuters)

Children react after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad near the Syrian Arab Red Crescent center in the Douma neighborhood of Damascus May 6, 2015. (Photo by Bassam Khabieh/Reuters)