output_description: Print the maximum possible value M of the final integer on the blackboard, and
  a sequence of operations x_i, y_i that maximizes the final integer, in the
  format below.
  
  Here x_i and y_i represent the integers x and y chosen in the i-th operation,
  respectively.
  
  If there are multiple sequences of operations that maximize the final integer,
  any of them will be accepted.
  
      
      
      M
      x_1 y_1
      :
      x_{N-1} y_{N-1}
      
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      A_1 A_2 ... A_N
attempt: n = int(input())
  v = list(map(int, input().split()))
  v.sort()
  h = n // 2
  print(sum(v[h:]) - sum(v[:h]))
  s = 0
  for i in range(n):
      if i % 2 == n % 2:
          x = v[i // 2]
      else:
          x = v[i // 2 + h]
      if i:
          print(x, s)
      s = x - s
  
problem_description: Statement
  
  There are N integers, A_1, A_2, ..., A_N, written on a blackboard.
  
  We will repeat the following operation N-1 times so that we have only one
  integer on the blackboard.
  
    * Choose two integers x and y on the blackboard and erase these two integers. Then, write a new integer x-y.
  
  Find the maximum possible value of the final integer on the blackboard and a
  sequence of operations that maximizes the final integer.
samples: [{"input": "3\n    1 -1 2", "output": "4\n    -1 1\n    2 -2\n    \n\nIf we choose x = -1 and y = 1 in the first operation, the set of integers\nwritten on the blackboard becomes (-2, 2).\n\nThen, if we choose x = 2 and y = -2 in the second operation, the set of\nintegers written on the blackboard becomes (4).\n\nIn this case, we have 4 as the final integer. We cannot end with a greater\ninteger, so the answer is 4.\n\n* * *"}, {"input": "3\n    1 1 1", "output": "1\n    1 1\n    1 0"}]