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;
class Main{
	public static void main(String[] a){
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		long num = n;
		while(n > 1){
			n--;
			num *= n;
		}
		System.out.println(num);
	}
}