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 <cstdio>

using namespace std;

int main(void){
	long long int n, mul = 1;
	scanf("%lld",&n);
	while(n){
		mul *= n;
		n--;
	}
	printf("%lld\n",mul);
	return 0;
}