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;
	int i;
	long long ans=1;

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

}