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
#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys
import math

for s in sys.stdin:
  d = int(s)
  print math.factorial(d)  