# rejection sampling

def f():
    var x, y, k, n
    while n > 0:
        k = 1
        while k > 0:
            prob(1,1):
                x = 0
            else:
                x = 1
            prob(1,1):
                y = 0
            else:
                y = 1
            if x = y:
                k = 1
            else:
                k = 0
            tick 1
        n = n - 1