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()
{
	long long int n,i,ret=1;
	cin>>n;
	for(i=n;i>=1;i--){
		ret *= i;
	}
	cout<<ret<<endl;
	
	return 0;
}