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 <cstdio>
using namespace std;
int main(){
    int n;unsigned long ans=1;
    scanf("%d", &n);
    while(n!=1){ans*=n;--n;}
    printf("%lu\n",ans);
    return 0;
}