text: '''
  Problem Statement: https://www.hackerrank.com/challenges/bon-appetit/problem
  @Coded by TSG,2020
  '''
  
  import math
  import os
  import random
  import re
  import sys
  
  # Complete the bonAppetit function below.
  def bonAppetit(bill, k, b):
      count=0
      for i in range(len(bill)):
          if(i!=k):
              count+=bill[i]
      pay = count//2
      if(pay != b):
          print(b-pay)
      else:
          print("Bon Appetit")
  
  if __name__ == '__main__':
      nk = input().rstrip().split()
  
      n = int(nk[0])
  
      k = int(nk[1])
  
      bill = list(map(int, input().rstrip().split()))
  
      b = int(input().strip())
  
      bonAppetit(bill, k, b)
  