Members of the New People's Army (NPA) female guerrillas perform a cultural show during the release of a Philippines army soldier in Sugbongcogon town, Misamis Oriental, southern Philippines, November 20, 2015. NPA spokesperson Allan Juanito warned that they will seize more soldiers to exchange them with the government as "Prisoners of war". (Photo by Froilan Gallardo/Reuters)

A man passes by an unfinished street art graffiti made in a stairway by French street artists Zag and Sia in Paris on March 1, 2016. The two artists drew inspiration from famous “Liberty Leading the People” (La Liberte guidant le peuple) painting by French Eugene Delacroix commemorating the July Revolution of 1830 and viewed as a symbol of the French Republic. (Photo by Joel Saget/AFP Photo)

An Armatix employee holds a “smart gun” by the company at the Armatix headquarters in Munich May 14, 2014. The gun is implanted with an electronic chip that allows it to be fired only if the shooter is wearing a watch that communicates with it through a radio signal. If the gun is moved more than 10 inches (25 cm) from the watch, it will not fire. A Maryland gun shop owner has dropped his plan to be the first in the United States to sell the so-called “smart gun” after a backlash that included death threats. (Photo by Michael Dalder/Reuters)

In this photo provided by Jean Revillard, Solar Impulse 2, a plane powered by the sun's rays and piloted by Andre Borschberg, approaches Kalaeloa Airport near Honolulu, Friday, July 3, 2015. His 120-hour voyage from Nagoya, Japan broke the record for the world's longest nonstop solo flight, his team said. (Photo by Jean Revillard/Global Newsroom via AP Photo)

People watch as an acrobat rides his motorcycle around a circular track at an entertainment park set up outside a shrine in Rawalpindi, Pakistan, on June 19, 2013. (Photo by Muhammed Muheisen/Associated Press)

Bob Steele, of Jefferson, Texas, positions his bears during The Great Bear Show at the Dubuque (Iowa) County Fair on July 25, 2012. (Photo by Jessica Reilly/Telegraph Herald)

Street vendors hold campaign posters for presidential candidate Patrice Talon ahead of the second round of Benin's presidential election on Sunday in Cotonou, Benin, March 18, 2016. (Photo by Charles Placide Tossou/Reuters)

Bottlenose dolphins swim over visitors in water tank at the Hakkeijima Sea Paradise aquarium-amusement park complex in Yokohama, southwest of Tokyo, Tuesday, July 21, 2015. Temperatures in Tokyo's metropolitan area neared around 96 degree Fahrenheit, or 35 degree Celsius, on Tuesday. (Photo by Shuji Kajiyama/AP Photo)