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 a;
long long sum=1;
	cin>>a;
	for (int i = a; i > 0; --i) {
		sum*=i;
	}
cout<<sum<<endl;
}