output_description: Print the maximum possible value of B_1 + B_2 + ... + B_N.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      A_1 A_2 ... A_N
attempt: N, *A = map(int, open(0).read().split())
  x, y = 0, -1e10
  for a in A:
      x, y = max(x + a, y - a), max(x - a, y + a)
  print(x)
  
problem_description: Statement
  
  There are N integers, A_1, A_2, ..., A_N, arranged in a row in this order.
  
  You can perform the following operation on this integer sequence any number of
  times:
  
  **Operation** : Choose an integer i satisfying 1 \leq i \leq N-1. Multiply
  both A_i and A_{i+1} by -1.
  
  Let B_1, B_2, ..., B_N be the integer sequence after your operations.
  
  Find the maximum possible value of B_1 + B_2 + ... + B_N.
samples: [{"input": "3\n    -10 5 -4", "output": "19\n    \n\nIf we perform the operation as follows:\n\n  * Choose 1 as i, which changes the sequence to 10, -5, -4.\n  * Choose 2 as i, which changes the sequence to 10, 5, 4.\n\nwe have B_1 = 10, B_2 = 5, B_3 = 4. The sum here, B_1 + B_2 + B_3 = 10 + 5 + 4\n= 19, is the maximum possible result.\n\n* * *"}, {"input": "5\n    10 -4 -8 -11 3", "output": "30\n    \n\n* * *"}, {"input": "11\n    -1000000000 1000000000 -1000000000 1000000000 -1000000000 0 1000000000 -1000000000 1000000000 -1000000000 1000000000", "output": "10000000000\n    \n\nThe output may not fit into a 32-bit integer type."}]