small = 0.001
def f(x):
return x*x*x-2*x-3
def calc(x1,x2):
xmid = (x1 + x2)/2
ymid = f(xmid)
if (ymid < -small) :
result = calc(xmid,x2)
else if (ymid > small) :
result = calc(x1,xmid)
else :
result = xmid
return result