People wearing costumes walk during Halloween in Sierra Madre, California, U.S., October 31, 2017. (Photo by Mario Anzuoni/Reuters)

A young woman holds her smartphone at Red Square with the Kremlin's Spasskaya Tower, right, and St. Basil Cathedral, center, in the background in Moscow, Russia, Monday, July 25, 2016. (Photo by Pavel Golovkin/AP Photo)

Children dressed up as Hindu Lord Krishna pose during Janmashtami festival celebrations marking the birth anniversary of Krishna in Agartala, India August 24, 2016. (Photo by Jayanta Dey/Reuters)

Nicki Minaj performs on stage during the 2017 NBA Awards Live On TNT on June 26, 2017 in New York City, USA. (Photo by Michael Loccisano/Getty Images for TNT)

Two cats watch a mouse walking on the pavement in Kuwait City on March 8,2017. (Photo by Yasser Al-Zayyat/AFP Photo)

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)

A Hawaiian cleaner wrasse provides its cleaning services to a yellowfin goatfish in a reef community off the Big Island in Hawaii. Cleaner species help rid their hosts of ectoparasites, dead tissue, bacteria and fungi. Studies have shown cleaning to play a vital role in keeping many reef ecosystems healthy. (Photo by Marty Snyderman/Caters News Agency)

Aegean airlines air hostesses take selfies after a news conference in Athens, Wednesday, March 28, 2018. In a deal worth up to $5 billion, Greek airline Aegean says it will buy 30 new Airbus aircraft, with the option of an additional 12, to upgrade its fleet as the country expects to break tourism records. The signing of the final purchase agreement is expected in June. (Photo by Petros Giannakouris/AP Photo)