#!/bin/python3

import math
import os
import random
import re
import sys

nk = input().rstrip().split()

item= int(nk[0])

allergy = int(nk[1])

bill = list(map(int, input().rstrip().split()))
back = int(input())
t = 0
total = 0
ret = 0

for i in range(0,item):
    if i!=allergy: 
    
        t = t + bill[i]
total = t/2

if back>total:
    ret = int(back - total)
    s = str(ret)
if total == back:
    s = "Bon Appetit"
print(s)
