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.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		BigInteger res = BigInteger.valueOf(1);
		for(int i = 1; i <= n; i++)
			res = res.multiply(BigInteger.valueOf(i));
		System.out.println(res);
	}
}