Children are engulfed by foam during the Bubble Show event in Beijing, China, Sunday, June 26, 2016. Thousands of residents enjoy colored foam churned out by machines along a running track at the event designed for children and parents' interaction. (Photo by Ng Han Guan/AP Photo)

A Hindu priest waits to perform prayers next to Tejas, India's first locally-built Light Combat Aircraft (LCA), before its induction into the Indian Air Force at the Hindustan Aeronautics Limited (HAL) Airport in Bengaluru, India, July 1, 2016. (Photo by Abhishek N. Chinnappa/Reuters)

A damaged vehicle is seen next to the ring road, around Skopje, near the village of Stajkovci, Skopje, The Former Yugoslav Republic of Macedonia, 08 August 2016. At least 21 people have died and more than 100 are injured in the heavy rain storm that hit the Macedonian capital Skopje late Saturday night causing severe damage to the roads and house infrastructure. More than 80 vehicles were hit by landslides at Skopje's ring road. The highway remains closed. The government announced a 15-day state of emergency in the Skopje and Tetovo region. (Photo by Georgi Licovski/EPA)

Jennifer Oeser of Germany competes in the Women's Heptathlon Long Jump on Day 8 of the Rio 2016 Olympic Games at the Olympic Stadium on August 13, 2016 in Rio de Janeiro, Brazil. (Photo by Alexander Hassenstein/Getty Images)

Puerto Rico's Grace Claxton warms up before competing in the Women's 400m Hurdles Round 1 during the athletics event at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 15, 2016. (Photo by Jewel Samad/AFP Photo)

A P-51 Mustang named “Charlotte's Chariot” from the Southern Heritage Air Foundation flies past a cloud of smoke and fire from a nearby battle reenactment during the Wings Over Houston Airshow in Houston, on Saturday, November 1, 2014. Battle reenactments are part of the yearly show held at Ellington Airport. (Photo by Kar Hlava/AP Photo/Bay Area Citizen)

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolish a section of the wall on November 11, 1989. (Photo by Gerard Malie/AFP Photo)

Syrians try to rescue a dead body under the debris of a collapsed building after Syrian and Russian army carried out an airstrike on opposition controlled residential area at Merce neighborhood of Aleppo, Syria on September 23, 2016. (Photo by Jawad al Rifai/Anadolu Agency/Getty Images)