Employees work at a sorting centre of Zhongtong (ZTO) Express ahead of the Singles Day shopping festival, Chaoyang District, Beijing, November 8, 2015. On China's giant Singles Day internet shopping festival, the country's delivery firms are stretched so thin that they are looking for tie-ups, listings and new investors to husband their resources. (Photo by Jason Lee/Reuters)

A police officer detains a woman on suspicion of collaborating with the 18th street gang during a "Safe House" operation at the Concepcion neighbourhood in San Salvador, July 2, 2015. Salvadoran police make “Safe House” operations at dangerous neighbourhoods of the capital to prevent murders, according to local media. (Photo by Jose Cabezas/Reuters)

South Korea's Black Eagles aerobatics team performs an aerial display forming a Ying and Yang logo during the Singapore Airshow at Changi exhibition center in Singapore on February 16, 2016. (Photo by Roslan Rahman/AFP Photo)

A fish jumps over a net as a boy works in a fish farm at Htantapin township, outside Yangon, Myanmar February 18, 2016. One in five children in Myanmar aged 10-17 go to work instead of school, according to figures from a census report on employment published last month, and the opening up of the economy since 2011 has triggered a spike in demand for labour. Many children work in fish farming and processing. At Yangon's San Pya fish market, the country's largest, girls and boys as young as nine clean and process fish and unload boats and trucks during 12-hour overnight shifts. (Photo by Soe Zeya Tun/Reuters)

Models prepare backstage ahead of the Strateas.Carlucci show at Mercedes-Benz Fashion Week Australia 2015 at Carriageworks on April 13, 2015 in Sydney, Australia. (Photo by Ryan Pierse/Getty Images)

North Koreans who signed up to join the army train in the midst of political tension with South Korea, in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang August 23, 2015. Top aides to the leaders of North and South Korea resumed talks on Sunday after negotiating through the night in a bid to ease tensions involving an exchange of artillery fire that brought the peninsula to the brink of armed conflict. (Photo by Reuters/KCNA)

American reality television personality, model and social media personality Kylie Jenner seen on June 16, 2018 in Los Angeles, California. (Photo by Splash News and Pictures)

Miss Talavera Bruce 2017, Mayana Rosa Alves, right, takes a cigarette break with two contestants before the start of the 13th annual Miss Talavera Bruce beauty pageant at the penitentiary the pageant is named for, in Rio de Janeiro, Brazil, Tuesday, December 4, 2018. Prison authorities say they organize the annual beauty contest to encourage self-esteem, fight idleness and promote integration among the female inmates. (Photo by Silvia Izquierdo/AP Photo)