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(void)
{
    long long int i,n,x=1;
    scanf("%lld",&n);
    for(i=1;i<=n;i++){
        x=x*i;
    }
    printf("%lld\n",x);
    return 0;
}