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

import java.io.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		long answer = 1;
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        String s = buf.readLine();
        long n = Integer.parseInt(s);
        for (int i = 1; i <= n;i++){
        	answer = answer * i;
        }
		System.out.println(answer);
		
	}
}