Children play in an outdoor shower as a soldier takes part in a surprise operation in the Manguinhos slum in Rio de Janeiro, Brazil, Thursday, January 18, 2018. Troops have been sent to Rio due to the increase of the violence, and in an attempt to help restore order, but so far have had little impact. The operation on Thursday took place three weeks ahead of Carnival, when thousands of tourists are expected to arrive in the city. (Photo by Leo Correa/AP Photo)

German carmaker Daimler's new Smart Fortwo car is seen on display during its world premiere in Berlin July 16, 2014. Daimler is betting that cooperation with Renault and the launch of models to tap growing demand for city cars may pave the way for its diminutive Smart brand to become profitable. Smart will add a new four-seater model to its lineup this year and upgrade the two-passenger Fortwo vehicle, raising hopes by the German group of boosting the brand's flagging sales. (Photo by Thomas Peter/Reuters)

Scientist Jiri Sindelar checks a ring of a Boreal owl chick outside the “Smart Nest Box”, which allows the study of birds by using mounted cameras, in a forest near the village of Mikulov, Czech Republic, June 18, 2016. (Photo by David W. Cerny/Reuters)

NATO and U.S. flags flutter as U.S. Air Force F-22 Raptor fighter flies over the military air base in Siauliai, Lithuania, April 27, 2016. (Photo by Ints Kalnins/Reuters)

A military police officer patrols in the Roquette Pinto shantytown, part of the Mare slum complex in Rio de Janeiro, Brazil, Wednesday, April 1, 2015. The Brazilian army has begun to pull out of one of Rio de Janeiro's most violent slums, with police assuming responsibility for security in the area. (Photo by Felipe Dana/AP Photo)

A Utah Valley University student walks down the bright green lanes painted on the stairs from the gym Thursday, June 18, 2015, at Utah Valley University, in Orem, Utah. Utah Valley University spokeswoman Melinda Colton said the green lanes were intended as a lighthearted way to brighten up the space and get students attention. (AP Photo/Rick Bowmer)

Omani Tactical & Commando personnel are seen during the month-long GCC joint security exercise “Arabian Gulf Security 1” in Manama, Bahrain November 1, 2016. “Arabian Gulf Security 1” exercises will continue until mid-November with the participation of the UAE, Saudi Arabia, Oman, Qatar and Kuwait. (Photo by Hamad I. Mohammed/Reuters)