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<iostream>
using namespace std;
int main(){
	int n,i;
	unsigned long long int ans=1;
	cin>>n;
	for(i=2;i<=n;i++){
		ans*=i;
	}
	cout<<ans<<endl;
	return 0;
}