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