# -*- coding: utf-8 -*-
def sqrt(a):
    if a < 0: raise ValueError('a doit être positif')
    if a == 0: return 0
    multiplier = 1
    while a >= 4:
        multiplier = multiplier * 2.0
        a = a / 4.0
    while a < 1:
        multiplier = multiplier / 2.0
        a = a * 4.0
    g = a + 0.0
    for i in range(10):
        g = (g + a / g) / 2
    return g * multiplier



print sqrt(2)