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 sc = new Scanner(System.in);
		while(sc.hasNextInt()){
		int n = sc.nextInt();
		long a = 1;
		if(n==0)a=0;
		for(;0<n;n--){
			a*=n;
		}
		System.out.println(a);
		}
	}
}