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
#include<stdio.h>
int main(){long long n,i;scanf("%lld",&n);for(i=n;--n;)i*=n;printf("%lld\n",i);}