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.*;
import java.lang.*;
import java.math.*;

public class Main {
	Scanner sc = new Scanner(System.in);
	long rep(long n){
		if(n == 0){
			return 1;
		}else{
			return rep(n-1)*n;
		}
	}
	void run(){
		int n = sc.nextInt();
		System.out.println(rep(n));
	}
	public static void main(String[] args){
		Main m = new Main();
		m.run();
		
	}
}