In this photo illustration a package of Nicotine Gum, which is advertised as helping people stop smoking cigarettes, is seen on January 10, 2012 in Miami, Florida. A study published in the journal Tobacco Control on Monday, reported that the nicotine alternatives, like Nicotine Gum, have no lasting effect on people trying to quit their smoking habit. (Photo illustration by Joe Raedle/Getty Images)

Children play at a makeshift camp for migrants and refugees at the Greek-Macedonian border near the village of Idomeni, Greece, March 29, 2016. (Photo by Marko Djurica/Reuters)

A model presents a creation by Chinese designer Hu Sheguang from Sheguang Hu collection at China Fashion Week in Beijing, March 31, 2016. (Photo by Jason Lee/Reuters)

Visitors walk through a tulip display in Chaya Mountain, Suiping County in Zhumadian, Henan Province of China on March 31, 2016. There are more than ten varieties of tulips here. (Photo by VCG/VCG via Getty Images)

Self-employed pedicab driver Danilo Guerra, 25, uses his mobile phone as he waits for clients in downtown Havana April 12, 2016. (Photo by Alexandre Meneghini/Reuters)

A model is reflected in a mirror as she applies make up backstage during Kazakhstan Fashion Week in Almaty, Kazakhstan, April 19, 2016. (Photo by Shamil Zhumatov/Reuters)

Eghy (L) uses his makeshift snorkel as his colleague lifts up green mussels to their boat in Jakarta Bay, Indonesia, April 20, 2016. (Photo by Reuters/Beawiharta)

A student protester throws a stone against a riot police vehicle during a demonstration to demand changes in the education system in Santiago, Chile, April 21, 2016. (Photo by Ivan Alvarado/Reuters)