bon apetite

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

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner scan = new Scanner(System.in);
        int items = scan.nextInt();
        int didNotEat = scan.nextInt();
        
        double[] costArray = new double[items];
        for(int i = 0; i < items; i++)
            costArray[i] = scan.nextDouble();
        
        int annaPaid = scan.nextInt();
        
        
      
        double runningCost = 0;
        
        for(int i = 0; i < items; i++){
            if(i == didNotEat)
                continue;
            else{
                runningCost += costArray[i] / 2.0;
            }
        }
        
        if((int)Math.round(runningCost) == annaPaid)
            System.out.print("Bon Appetit");
        else
            System.out.print(annaPaid - (int)Math.round(runningCost));
       
    }
}