# t15 in C4B figure 8

def f():
    var x, y, t, r
    assume y >= 0
    while [y >= 0] x > y:
    	x = x - y
    	x = x - 1
    	t = y
    	while t > 0:
        	r = unif(0,1)
        	t = t - r
        	tick 1

    	tick 1