Using Static

import java.util.Scanner;
public class Main{
    static int fac(int n){
        if(n==0||n==1) return 1;
        return n*fac(n-1);
    }
    public static void main(String args[]){
        Scanner cin = new Scanner(System.in);
        while(cin.hasNext()){
            int n = cin.nextInt();
            System.out.println(fac(n));
        }
    }
}