Revellers celebrate “Ash Monday” by participating in a colourful “flour war”, a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter,in the port town of Galaxidi, Greece, February 27, 2017. (Photo by Alkis Konstantinidis/Reuters)

Revellers celebrate “Ash Monday” by participating in a colourful “flour war”, a traditional festivity marking the end of the carnival season and the start of the 40-day Lent period until the Orthodox Easter, in Galaxidi, Greece February 19, 2018. (Photo by Alkis Konstantinidis/Reuters)

Students from St Andrews University indulge in a tradition of covering themselves with foam to honour the “academic family” on the lower college lawn on October 23, 2017, in St Andrews, Scotland. (Photo by Jeff J. Mitchell/Getty Images)

A U.S. Army soldier with the 10th Special Forces Group and his military working dog jump off the ramp of a CH-47 Chinook helicopter from the 160th Special Operations Aviation Regiment during water training over the Gulf of Mexico as part of exercise Emerald Warrior 2011 on March 1, 2011. (Photo by Tech. Sgt. Manuel J. Martinez/U.S. Air Force)

A Philippine boy collects used plastic bottles to be sold at a junk shop at Divisoria market in Manila on November 29, 2017. (Photo by Noel Celis/AFP Photo)

A young girl works at a construction site in Patiala district, Rajpura, India on November 20, 2019. (Photo by Saqib Majeed/Barcroft Media)

A relative of a Chinese passenger aboard the Malaysia Airlines MH370, covers his face after being told the latest update in Beijing, China, Monday, March 24, 2014. A new analysis of satellite data indicates the missing Malaysia Airlines plane crashed into a remote corner of the Indian Ocean, Malaysian Prime Minister Najib Razak said Monday. The news is a major breakthrough in the unprecedented two-week struggle to find out what happened to Flight 370, which disappeared shortly after takeoff from Kuala Lumpur to Beijing with 239 passengers and crew aboard on March 8. (Photo by Ng Han Guan/AP Photo)