People dance Tuesday, April 28, 2015, in Baltimore. Maryland's governor vowed there would be no repeat of the looting, arson and vandalism that erupted Monday in some of the city's poorest neighborhoods. (Photo by Matt Rourke/AP Photo)

Party-goers partake in a festival better known as Holi One, during International Workers Day in Johannesburg, South Africa, 01 May 2015. The colour festival promotes togetherness as well as colourness in everday life. May Day is observed worldwide every year on 01 May. (Photo by Kevin Sutherland/EPA)

Sepak Takraw – ISTAF Super Series Korea 2014-15 – Gunsan City, South Korea April 26, 2015: Thailand's Fueangfa (L) in action during the final. (Photo by Jeremy Lee/Reuters)

A handout photograph provided by Brian Kubicki of Costa Rican Amphibian Research Center on 26 April 2016 shows a “Crystal frog”, Hyalinobatrachium dianae (H. diane). This frog was discovered by US biologist Brian Kubicki and Costa Ricans Stanley Salazar and Robert Puschendorf in a rainy forest of Costa Rican caribbean after 40 years without notice of any new example of this kind. (Photo by Brian Kubicki/EPA/Costa Rican Amphibian Research Center)

A group of youngsters dressed as ghouls and zombies for Halloween parade in downtown Lisbon, Portugal, Friday, October 31, 2014. (Photo by Francisco Seco/AP Photo)

Hundreds of festive, adorable canines and their owners took part in the annual “A Very Corgi Howloween” costume walk Saturday, October 25, 2014, at Green Lake in Seattle, Wash. The walk was put on by the Seattle-local “Corgi's R Us” MeetUp group. (Photo by Jordan Stead/AP Photo/Seattlepi.com)

Vladislav Doronin and Naomi Campbell attend the religious ceremony of the Royal Wedding of Prince Albert II of Monaco to Princess Charlene of Monaco in the main courtyard at the Prince's Palace on July 2, 2011 in Monaco. The Roman-Catholic ceremony follows the civil wedding which was held in the Throne Room of the Prince's Palace of Monaco on July 1. With her marriage to the head of state of the Principality of Monaco, Charlene Wittstock has become Princess consort of Monaco and gains the title, Princess Charlene of Monaco. Celebrations including concerts and firework displays are being held across several days, attended by a guest list of global celebrities and heads of state. (Photo by Sean Gallup/Getty Images)

A fellow officer comes to the aid of injured patrolman C.V. Satt, who was pelted with rocks and beer bottles during a clash between police and relief demonstrators in Denver September 23, 1935. (Photo by Henry G. Eisenhand/AP Photo)