import math


def factorial_for(x):
    result = 1
    for i in range(2, x + 1):
        result *= i
    return result


def factorial_while(x):
    result = 1
    while x > 1:
        result *= x
        x -= 1
    return result


def factorial_recursive(x):
    if x == 0:
        return 1
    else:
        return x * factorial_recursive(x - 1)


math.factorial(5)