A woman greets a street artist at the San Fermin festival in Pamplona, northern Spain July 8, 2016. (Photo by Eloy Alonso/Reuters)

Law enforcement officers clash with protesters, Wednesday, July 20, 2016, in Cleveland, during the third day of the Republican convention. (Photo by John Minchillo/AP Photo)

A combination photo shows various popular street foods under $6 from various hawker food stalls and eateries in Singapore, taken between July 28 to 31, 2016. Top row (L to R) bak chor mee, soya sauce chicken; Middle row (L to R) laksa, hokkien mee, nasi lemak, ice kachang; Bottom row (L to R) rojak, roti prata and satay. (Photo by Edgar Su/Reuters)

As the sun rises, Gentoo penguins start their day on Wednesday, February 17, 2016, on Sea Lion Island, Falkland Islands. Sea Lion Island, which lies about 10 miles to the south of mainland East Falkland, is the southern most human-inhabited island of the more than 750 islands and islets of the Falkland Islands. (Photo by Jahi Chikwendiu/The Washington Post)

A military instructor helps a boy to shoot a rifle with blanks at a weapon exhibition during a military show in St.Petersburg, Russia, Sunday, January 17, 2016. (Photo by Dmitry Lovetsky/AP Photo)

A child coughs as migrants and refugees run away after Macedonian police fired tear gas at hundreds of Iraqi and Syrian migrants who tried to break through the Greek border fence in Idomeni, on February 29, 2016. Greek police said more than 6,000 people were massed at the border, in a buildup triggered by Austria and Balkan states capping the numbers of migrants entering their territory. (Photo by Louisa Gouliamaki/AFP Photo)

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)

A woman poses for a photographer (not pictured) as a man sits next to her in downtown Catania, Italy April 20, 2016. (Photo by Tony Gentile/Reuters)