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