A man salts a downtown sidewalk in Washington, Thursday, March 5, 2015, as snow begins to fall. The U.S. federal government said its offices in the Washington area will be closed Thursday because of a new round of winter weather expected in the region. The Office of Personnel Management said non-emergency personnel in and around Washington were granted excused absences for the day. Emergency employees and telework-ready employees were expected to work. (AP Photo/Andrew Harnik)

In this October 21, 2015, file photo, a young man rides a hoverboard along a Manhattan street toward the Empire State Building in New York. More than 500,000 hoverboards are being recalled after reports that they can burst into flames. The Consumer Product Safety Commission said Wednesday, July 6, 2016, it has received 99 reports of battery packs in the two-wheel motorized scooters catching fire or exploding that causing burns or property damage. The recalled hoverboards were made by eight companies. (Photo by Kathy Willens/AP Photo)

A visitor takes pictures with a smartphone of an artwork entitled “Blue Europe, 2015” by Chinese artist Liu Bolin, on display during the exhibition “Visible Invisible” at the Mudec Museum in Milan on May 14, 2019. Liu Bolin known as “the invisible man” for his photographic self-portraits, focused on a body-painting blending with the surrounding area. (Photo by Miguel Medina/AFP Photo)

A man holds up for a picture a one hundred trillion Zimbabwean dollars note inside a shop in Harare, Zimbawe, June 12, 2015. Hyperinflation in Zimbabwe was a period of currency instability that began in the late 1990s shortly after the confiscation of private farms from landowners, towards the end of Zimbabwean involvement in the Second Congo War. During the height of inflation from 2008 to 2009, it was difficult to measure Zimbabwe's hyperinflation because the government of Zimbabwe stopped filing official inflation statistics. However, Zimbabwe's peak month of inflation is estimated at 79.6 billion percent in mid-November 2008. (Photo by Philimon Bulawayo/Reuters)

Indian women wearing traditional attire take a “selfie” with an Indian man dressed as King 'Mahabali' during the Hindu harvesting festival Onam celebrations in Bangalore, India, 28 August 2015. Local people put flower mats in front of their houses, to welcome the King Mahabali, a past ruler of Kerala southern India, during the ten-day festival. (Photo by Jagadeesh N. V./EPA)

A man rides through the flames on a horse during the “Luminarias” annual religious celebration on the eve of Saint Anthony's Day in the village of Alosno, southwest Spain, January 16, 2015. According to a tradition that dates back 500 years, people ride their horses through the narrow cobblestone streets of this small village to purify the animals with the smoke of the bonfires. Saint Anthony is the patron of animals. (Photo by Marcelo del Pozo/Reuters)

A member of the Community Police of the FUSDEG (United Front for the Security and Development of the State of Guerrero) search for a man, who ran away upon seeing the Community Police approach as they patrolled a street, in the village of Petaquillas, on the outskirts of Chilpancingo, in the Mexican state of Guerrero, February 1, 2015. Approximately 500 members of the Community Police from the FUSDEG took control of the security of the village of Petaquillas on the night of January 30 at the request of the people tired of the actions of organized crime, local media reported. (Photo by Jorge Dan Lopez/Reuters)

An Afghan policeman carries a wounded man at the site of a suicide attack in Kabul March 25, 2015. Six people were killed and more than 30 injured in the suicide bombing in the Afghan capital on Wednesday that struck close to the presidential palace in the heart of the city, the Interior Ministry said. The suicide bomber had been travelling in a vehicle packed with explosives and it was not immediately clear what the target of the attack had been. (Photo by Omar Sobhani/Reuters)