Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)
from sys import stdin
from math import factorial
print(factorial(int(stdin.readline())))