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 n,a;
	cin>>n;
	a = n;
	while(true){
		n = n-1;
		if (n == 0)break;
		a = a*n;
	}cout<<a<<endl;
}