#!/usr/local/cpython-3.4/bin/python3

'''Compute a factorial'''

# pylint: disable=superfluous-parens
# superfluous-parens: Parentheses are good for clarity and portability

import sys

def factorial(number):
    '''Compute factorial of number'''
    integer = int(number)
    assert integer >= 1
    result = 1
    for factor in range(2, integer + 1):
        result *= factor
    return result

def main():
    '''Main function'''
    number = int(sys.argv[1])
    result = factorial(number)
    print(result)

main()