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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main {

	public static void main(String[] a){

		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));

		String tmpString = null;

		try {
			if(null != (tmpString = bf.readLine())){
				long ans = qa(Integer.parseInt(tmpString));
				System.out.println(ans);
			}
		} catch (IOException e) {
		}
	}

	private static long qa(int number){
		if(number == 1)return number;
		return number * qa(number - 1);
	}
}