from math import sqrt

def fibo(n):
    atual, prox = 0, 1
    for i in range(n):
        atual, prox = prox, atual+prox
    return atual

fi = (1+sqrt(5))/2
psi = (1-sqrt(5))/2
inv_raiz_5 = 1/sqrt(5)

def binet(n):
    return int(inv_raiz_5 * (fi**n - psi**n))