import math

def mySqrt(S):
    x_new = S / 2.0
    condition = True
    while condition:
        x_old = x_new
        x_new = (x_old + S / x_old) / 2.0
        condition = x_new != x_old
    return x_new


print(mySqrt(5))
print(math.sqrt(5))