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
'''
Created on Mar 22, 2013

@author: wukc
'''
from sys import stdin

n=int(stdin.readline())
ans=1
for i in range(1,n+1):
    ans*=i
print(ans)