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 ans = BigInteger.ONE;
		for(int i=1;i<=n;i++) {
			ans=ans.multiply(BigInteger.valueOf(i));
		}
		System.out.println(ans);
	}
}