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

int main() {
	int n;
	cin>>n;
	long i,s=1;
	for(i=1;i<=n;i=i+1){
		s=s*i;
	}
	cout<<s<<endl;
}