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 n;
long p=1;

scanf("%d",&n);
for(int i=1;i<=n;i++)
p=p*i;

printf("%ld\n",p);
return 0;

}