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(){
    int i,n;
    unsigned long long f=1;
    scanf("%d",&n);
    for(i=2;i<=n;i++){
        f*=i;
    }
    printf("%lld\n",f);
}