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>
long long int f(int n){
if(n==1)return 1;
else return f(n-1)*n;
}
int main(){
int n;
scanf("%d",&n);
printf("%lld\n",f(n));
}