import java.util.Scanner;

public class LabProgram {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      
      /* Type your code here. */ 
      VendingMachine myVendingMachine = new VendingMachine();
      int Amount = scnr.nextInt();
      int Bottles = Amount;
      myVendingMachine.purchase(Bottles - Amount);
      myVendingMachine.restock(Bottles + Amount);
      myVendingMachine.purchase(Bottles - Amount);
      myVendingMachine.report();
      
   }
}

// simulates a simple vending machine with operations to purchase drinks and check inventory.
public class VendingMachine {
   
   // number of bottle in stock
   private int bottles;
   
   // initial inventory is 20
   public VendingMachine(){
      bottles = 20;
   }

   public void purchase(int amount){
      bottles = bottles - amount;
   }
  
   public int getInventory(){
      return bottles;
   }

   public void restock(int amount){
      bottles = bottles + amount;
   }
 
   public void report(){
      System.out.println("Inventory: " + bottles + " bottles");
   }
   
}