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.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		System.out.println(fact(n));
	}
	static long fact(long n) {
		if (n == 0) {
			return 1;
		} else {
			return n * fact(n - 1);
		}
	}
}

