import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Main {
 static int  Factorial(int n){
     if (n==0)
     {
         //bcoz 0 and 1 factorial is 1
         
         return 1;
     }
  
    int d =  Factorial(n-1);
    int multi = n * d;
    
    System.out.println(multi);
 
    return multi;
   
 
     
 }
 
 
 
    public static void main(String[] args) {
        System.out.println("Hello world!");
  
  
       int answer =   Factorial (5);
        System.out.println(answer);
  
  
  
    }
}