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
//0019
#include <bits/stdc++.h>
using namespace std;

int main(){
	double n,ans = 1;
	for(cin>>n;n != 0;n--){
	ans *= n;
}
	printf("%.f\n",ans );
	return 0;
}