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: # 入力が10**5とかになったときに100ms程度早い
  import sys
  
  read = sys.stdin.readline
  
  
  def read_ints():
      return list(map(int, read().split()))
  
  
  def read_a_int():
      return int(read())
  
  
  def read_matrix(H):
      """
      H is number of rows
      """
      return [list(map(int, read().split())) for _ in range(H)]
  
  
  def read_map(H):
      """
      H is number of rows
      文字列で与えられた盤面を読み取る用
      """
      return [read() for _ in range(H)]
  
  
  def read_col(H, n_cols):
      """
      H is number of rows
      n_cols is number of cols
  
      A列、B列が与えられるようなとき
      """
      ret = [[] for _ in range(n_cols)]
      for _ in range(H):
          tmp = list(map(int, read().split()))
          for col in range(n_cols):
              ret[col].append(tmp[col])
  
      return ret
  
  
  N = read_a_int()
  A = read_ints()
  
  # 最初にすべてのマイナスが外せないか試して、
  # abs最小の数に-をつけて合計すればいいんだ！
  
  # 問題はどうやってすべてのマイナスがはずせるか判別するか
  # +-+,---っていうパターンがあったらアウト
  flg = False
  for a1, a2, a3 in zip(A, A[1:], A[2:]):
      if a1 > -1 and a2 < 0 and a3 > -1:
          flg = True
      if a1 < 0 and a2 < 0 and a3 < 0:
          flg = True
  
  anstmp = sum([abs(a) for a in A])
  if not flg:
      print(anstmp)
      exit()
  
  # else
  mi = 10**9
  for a in A:
      mi = min(mi, abs(a))
  
  print(anstmp - 2 * mi)
  
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."}]