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.*;
public class Main{
    static Scanner kbd = new Scanner(System.in);
    public static void main(String[] args){
	while(kbd.hasNext()){
	    solve();
	}
    }
    
    static void solve(){
	long n = kbd.nextInt();
	long ans = fact(n);
	System.out.println(ans);
    }

    static long fact(long n){
	if(n==1) return 1;
	return n*fact(n-1);
    }
}