51 users have solved this problem:

spdskatr, he, Gomango999, testcoder, iamnumber4, dumpy, evanl, henryho2, lion, hoangxuanbach, Tuanlinh123, hiennoob, minhnhatnoe, binhphuc, bidepzai1510, Fong, tung, Lvl9001Wizard, user, hhyfirst, Yichen, programmer123, dorian, legendneverdie, loctildore, numb3r5, Philip_cpp, PeaceOfCake, Andy, JerryTheBerry, AlphaTao, Nosna, Double_Slash, 26yangri, jmuzhen, Sirhc_47, anson, Ghetto, aerobull42, pony_joe1, ad_red, Uasoni2, caterpillow, Lithanium, Supermarine_Spitfire, TheEpicCowOfLife, OoogaDooga, dusky, sssss, doantronganh2008, wap