Members of the U.S. Army 173rd Airborne Brigade stand at attention as a Ukrainian folk dance group performs at the opening ceremony of the “Rapid Trident” NATO military exercises on September 15, 2014 near Yavorov, Ukraine. The two-week exercises include participating units from a variety of NATO and NATO-associate countries as well as Ukrainian troops. Meanwhile fighting between pro-Russian separatists and Ukrainian armed foces has flared again in eastern Ukraine in a battle for the control of Donetsk airport despite the tenuous ceasefire. (Photo by Sean Gallup/Getty Images)

Models clad in costumes of video game charactors pose at a game booth during the Tokyo Game Show 2016 in Chiba, suburb of Tokyo, on September 15, 2016. Sony took centre stage at the annual four-day event, with its virtual reality headset ready to hit store shelves for the Christmas shopping season. (Photo by Toru Yamanaka/AFP Photo)

A protester clashes with a police officer in Athens' central Syntagma (Constitution) Square in this June 15, 2011 file photo. Greece triggered the regional financial crisis in 2009 when a far higher budget deficit than previously calculated emerged. The collapse of talks with creditors in Paris last November set off a month-long sequence of events leading to elections this week and proving Greece is still the region's weak link. The vote is expected to be won by Syriza, a far-left party opposed to the bailout, worrying investors and creditors alike. (Photo by Yannis Behrakis/Reuters)

Team Strong Silvers member Ngai Hin Kwok, 66, works out as teammate Ng Siu Chi, 57, watches at a stadium in Singapore March 15, 2015. Team Strong Silvers, is a group of senior citizens who train in calisthenics. The trio trains individually at least three times a week, and meets up for joint calisthenics at least twice a month. (Photo by Edgar Su/Reuters)

Japanese artist Megumi Igarashi, known as Rokudenashiko, holds her artwork after a news conference following a court appearance in Tokyo April 15, 2015. A Japanese artist on trial for obscenity after making figurines and a kayak modeled on her v*gina said on Wednesday that there was nothing wrong with her artwork and her arrest merely showed how far Japan remains behind the west. Words in the artwork read “Centre. 3D scan”. (Photo by Toru Hanai/Reuters)

A policeman controls traffic at 42nd Street and 7th Avenue as New York City remains without electricity caused by a blackout that affected the entire city and most of the eastern part of the nation August 15, 2003 in New York, New York. More than 50 million people were affected by the outage, in Toronto, Detroit, Cleveland and New York City. (Photo by Jose Jimenez/Primera Hora/Getty Images)

A suspected Vietcong is kicked by a Vietnamese soldier holding a rifle as another soldier attempts to tie his hands on October 22, 1965. The prisoner was one of 15 captured October 21 near Xom Chua when government troops raided in the plain of reeds area. Troops killed 43 suspected Vietcong and seized some arms. (Photo by Richard Merron/AP Photo)

An injured vulture is treated at the VulPro Vulture Rehabilitation Centre in Hartebeepoortdam in the Magalisburg region on September 15, 2015. Confined to southern Africa, just under 4,000 breeding pairs of Cape Vultures remain in the wild, mostly in South Africa, Lesotho and Botswana. Unless conservation efforts are successful, Africa's largest vulture species may be facing eventual extinction. (Photo by Mujahid Safodien/AFP Photo)