Soviet Army soldiers sit on their tanks in front of the Czechoslovak Radio station building in central Prague during the first day of Soviet-led invasion to then Czechoslovakia on August 21, 1968. (Photo by Libor Hajsky/Reuters)

Canada's Mandy Marchak (R) is taken down by France's Pauline Biscarat during the final match of the Hong Kong Sevens rugby women's invitational cup in Hong Kong March 28, 2014. (Photo by Tyrone Siu/Reuters)

Four-month-old fox cubs squaring up to each other in Walthamstow, England on August 7, 2015. (Photo by Greg Morgan/Barcroft Media)

A person poses on the track during a fashion competition at the Durban July horse racing event in Durban, South Africa, July 2, 2016. (Photo by Rogan Ward/Reuters)

A woman already appears to be regretting her choice of heels for the day out during the Grand National Festival at Aintree Racecourse on April 8, 2017 in Liverpool, England. (Photo by Alamy Stock Photos)

A protester dressed as a clown holds an umbrella over a Swiss police officer on a motorbike during a May Day demonstration in Zurich, Switzerland on May 1, 2017. (Photo by Arnd Wiegmann/Reuters)

Costumed characters participate in the 30th annual Dragon Con Parade in Atlanta, Georgia, USA, 03 September 2016. Thousands of attendees crowd downtown Atlanta hotels and streets during the Labor Day weekend for the Dragon Con science fiction and fantasy convention, many dressed as their favorite characters. (Photo by Erik S. Lesser/EPA)

A man sits in the back of a taxi with a goat after purchasing it from a livestock market ahead of the Eid al-Adha festival in Kolkata, India, September 8, 2016. (Photo by Rupak De Chowdhuri/Reuters)