Portuguese runner Adriele Silva gestures during the Great Wall Marathon at the Huangyaguan section of the Great Wall of China, in Jixian of Tianjin, China May 19, 2018. (Photo by Jason Lee/Reuters)

A U.S. Marine leads training on a shooting range in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)

A woman is tattooed during the Great British Tattoo Show in Alexandra Palace in north London, Britain May 23, 2015. (Photo by Neil Hall/Reuters)

A contestant walks the runway during 2017 Miss Great Britain competition at the Mayfair A-list venue DSTRKT on May 11, 2017 in London, England. The pageant hopefuls were battling it out to represent Miss Central London. Miss Great Britain is a female beauty pageant. It is the oldest pageant in the UK, established in 1945. Following World War Two, a number of seaside resorts around the country introduced beauty contests as attractions. (Photo by Jules Annan/Barcroft Images)

People use snowshoes during a tour of the Great Kemeri Bog, Latvia, October 17, 2015. The Kemeri bog is more than 8,000 years old and is one of the largest dry moss swamps in the Baltics. A more than decade-long joint restoration of the bog by the European Union and the Latvian government helped the bog recover its high moss marshes, damp black alder forests, floodplain meadows and seaside lakes – features now considered rare in Europe due to industrialisation. (Photo by Ints Kalnins/Reuters)

Yang Juan, an employee at Goopal Group, takes a nap in her seat after lunch, in Beijing, China, April 21, 2016. Office workers sleeping on the job is a common sight in China, where a surplus of cheap labour can lead to downtime at work. But in China's technology sector, where business is growing faster than many start-up firms can hire new staff, workers burn the midnight oil to meet deadlines and compete with their rivals. Some companies provide sleeping areas and beds for workers to rest during late nights. (Photo by Jason Lee/Reuters)

People take part in a half naked Santa run in downtown Budapest, Hungary, December 9, 2018. The partakers danced, ran, walked and laughed on the streets of Budapest, while others opted to simply raise money for the chosen charity. Many people had the names of their charities written on their bellies, while others were dressed in full Santa outfits. (Photo by Bernadett Szabo/Reuters)

A protester uses molotov cocktails against riot police during May Day protests on May 1, 2010 in Athens, Greece. (Photo by Milos Bicanski /Getty Images)