new_contents: def computeAnnaBill(k, costs):
      return sum(cost / 2.0 if index != k else 0.0 for index, cost in enumerate(costs))
  
  eps     = 1e-12
  n, k    = map(int, input().split())
  costs   = [int(cost) for cost in input().split()]
  
  charged = int(input())
  actual  = computeAnnaBill(k, costs)
  
  diff    = charged - actual
  
  if abs(diff) < eps:
      print('Bon Appetit')
  else:
      print('{:g}'.format(diff))
  
subject: Create solution.py