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mas = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]
num = 3

while len(mas) != 0:
    i = len(mas)/2
    if num == mas[i]:
        print mas[i],'- hooray!'
        break
    elif num < mas[i]:
        del mas[i:]
    else:
        del mas[:i+1]