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.Scanner;

public class Main {
public static void main(String[] args) {
  Scanner in = new Scanner(System.in);
  while (in.hasNext())
	System.out.println(f(in.nextInt()));
}

static long f(long v) {
  return (v == 1) ? 1 : f(v - 1) * v;
}
}