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(void){
	int n;
	int i;
	long long sum;
	cin>>n;
	sum=1;
	while(n>0){
		sum*=n;
		n--;
	}
	cout<<sum<<endl;
	return 0;
}
