The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)

In this photo taken late Thursday, May 7, 2015, a prison guard, left, and seated inmates cast shadows on a wall while waiting for the beginning of a rock concert by Romanian band Pro Musica, inside the Popa Sapca jail in Timisoara, western Romania. (Photo by Adi Piclisan/AP Photo)

A truck creates a wake as its driver tries to navigate a severely flooded street as heavy rains pour down Monday, September 8, 2014, in Phoenix. Storms that flooded several Phoenix-area freeways and numerous local streets during the Monday morning commute set an all-time record for rainfall in Phoenix in a single day. (Photo by Ross D. Franklin/AP Photo)

Lazar and his sister Andjelka sit by a candle in their home in the eastern Serbian town of Majdanpek, December 4, 2014. Electricity workers in Serbia struggled through snow, ice and treacherous terrain on Thursday to restore electricity to an eastern town left shivering without power, heating or running water for a fourth day. (Photo by Marko Djurica/Reuters)

Just Dance 2017 performance at Ubisoft E3 2016 – Day 2 at the Los Angeles Convention Center on Tuesday, June 14, 2016, in Los Angeles. (Photo by Dan Steinberg/Invision for Ubisoft/AP Images)

Labourers work at the installation site of Liquefied Petroleum Gas (LPG) pipeline on May Day or Labour Day in Chandigarh, India, May 1, 2015. (Photo by Ajay Verma/Reuters)

Rickshaw drivers wade through a flooded road after heavy rains swept through Guwahati, in the northeastern Indian state of Assam, on June 26, 2014. Seven people have been killed there in flash floods, landslides and heavy rainfall, local media reported Friday. (Photo by Utpal Baruah/Reuters)

A farmer seen harvesting his crops while Mount Sinabung spewing out volcanic ash on July 4, 2017 in North Sumatera, Indonesia. The increased volume of lava dome that reaches one million eight hundred cubic meters, said volcanologist, through radio communications, do not dampen the activities of the people around sinabung, such as farming, harvesting their crops, picking up objects that are still left behind, or just take a picture while walking around near mount Sinabung. (Photo by Sabirin Manurung/Pacific Press/Barcroft Images)