this function mean a*b, z is x time multiply.
def naive(a, b):
x = a; y = b
z = 0
while x > 0:
z = z + y
x = x - 1
return z
print(naive(4, 5))
def russian(a, b):
x = a; y = b
z = 0
while x > 0:
if x % 2 == 1: z = z + y
y = y << 1
x = x >> 1
return z
print(russian(5, 5))
