output_description: Print the maximum possible score of a'.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      a_1 a_2 ... a_{3N}
attempt: # 3N numbers
  n = int(input())
  lists = list(map(int, input().split()))
  second = lists.copy()
  second = second[::-1]
  for i in range(3 * n):
      second[i] = -second[i]
  MAX = sum(lists[:n])
  MIN = -sum(second[:n])
  MAXlist = [0 for i in range(n + 1)]
  MINlist = [0 for i in range(n + 1)]
  MAXlist[0] = MAX
  MINlist[0] = MIN
  ANS = -(10**100)
  import heapq
  
  a = lists[:n]
  b = second[:n]
  heapq.heapify(a)  # リストを優先度付きキューへ
  for j in range(n, 2 * n):
      heapq.heappush(a, lists[j])  # 要素の挿入
      heapq.heappush(b, second[j])
      mini = heapq.heappop(a)  # 最小値の取り出し
      mini2 = heapq.heappop(b)
      MAX -= mini
      MIN += mini2
      MAX += lists[j]
      MIN -= second[j]
      MAXlist[j + 1 - n] = MAX
      MINlist[j + 1 - n] = MIN
  MINlist = MINlist[::-1]
  for i in range(n + 1):
      ANS = max(ANS, MAXlist[i] - MINlist[i])
  print(ANS)
  
problem_description: Statement
  
  Let N be a positive integer.
  
  There is a numerical sequence of length 3N, a = (a_1, a_2, ..., a_{3N}). Snuke
  is constructing a new sequence of length 2N, a', by removing exactly N
  elements from a without changing the order of the remaining elements. Here,
  the score of a' is defined as follows: (the sum of the elements in the first
  half of a') - (the sum of the elements in the second half of a').
  
  Find the maximum possible score of a'.
samples: [{"input": "2\n    3 1 4 1 5 9", "output": "1\n    \n\nWhen a_2 and a_6 are removed, a' will be (3, 4, 1, 5), which has a score of (3\n+ 4) - (1 + 5) = 1.\n\n* * *"}, {"input": "1\n    1 2 3", "output": "-1\n    \n\nFor example, when a_1 are removed, a' will be (2, 3), which has a score of 2 -\n3 = -1.\n\n* * *"}, {"input": "3\n    8 2 2 7 4 6 5 3 8", "output": "5\n    \n\nFor example, when a_2, a_3 and a_9 are removed, a' will be (8, 7, 4, 6, 5, 3),\nwhich has a score of (8 + 7 + 4) - (6 + 5 + 3) = 5."}]