output_description: Print the number of choices of the integer K that make the number of problems
  for ARCs and the number of problems for ABCs the same.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      d_1 d_2 ... d_N
attempt: n = int(input())
  A = [int(a) for a in input().split()]
  A.sort(reverse=True)
  len = n // 2
  print(A[len] - A[len - 1])
  
problem_description: Statement
  
  Takahashi made N problems for competitive programming. The problems are
  numbered 1 to N, and the difficulty of Problem i is represented as an integer
  d_i (the higher, the harder).
  
  He is dividing the problems into two categories by choosing an integer K, as
  follows:
  
    * A problem with difficulty K or higher will be _for ARCs_.
    * A problem with difficulty lower than K will be _for ABCs_.
  
  How many choices of the integer K make the number of problems for ARCs and the
  number of problems for ABCs the same?
samples: [{"input": "6\n    9 1 4 4 6 7", "output": "2\n    \n\nIf we choose K=5 or 6, Problem 1, 5, and 6 will be for ARCs, Problem 2, 3, and\n4 will be for ABCs, and the objective is achieved. Thus, the answer is 2.\n\n* * *"}, {"input": "8\n    9 1 14 5 5 4 4 14", "output": "0\n    \n\nThere may be no choice of the integer K that make the number of problems for\nARCs and the number of problems for ABCs the same.\n\n* * *"}, {"input": "14\n    99592 10342 29105 78532 83018 11639 92015 77204 30914 21912 34519 80835 100000 1", "output": "42685"}]