output_description: Print the maximum possible value of s.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      D_1 D_2 ... D_N
attempt: import copy
  
  
  def minTG(TG):
      indexes1 = [i for i, x in enumerate(TG) if x == 1]
      indexes2 = [i for i, x in enumerate(TG) if x == 2]
      TG24 = [1] + [0] * 23
      if 12 in indexes1:
          indexes1.pop(-1)
          TG24[12] = 1
      for i in indexes1 + indexes2:
          TG24[i], TG24[24 - i] = 1, 1
  
      ans = 0
      for i in range(2 ** len(indexes1)):
          TG24c = copy.copy(TG24)
          bit = i
          for j in range(len(indexes1)):
              if bin(bit >> (j + 1))[-1] == "1":
                  TG24c[indexes1[j]] = 0
              else:
                  TG24c[24 - indexes1[j]] = 0
          temp = minTG_search(TG24c)
          if ans < temp:
              ans = temp
      return ans
  
  
  def minTG_search(TG24):
      s, temp, i = 24, 0, 1
      while i < 24:
          if TG24[i] == 1:
              if i - temp < s:
                  s = i - temp
              temp = i
          i += 1
      if 24 - temp < s:
          s = 24 - temp
      return s
  
  
  N = int(input())
  D = sorted(list(map(int, input().split())))
  TG = [0] * 13
  for i in range(N):
      TG[D[i]] += 1
  
  if TG[0] > 0 or max(TG) > 2:
      print(0)
  else:
      print(minTG(TG))
  
problem_description: Statement
  
  In CODE FESTIVAL XXXX, there are N+1 participants from all over the world,
  including Takahashi.
  
  Takahashi checked and found that the _time gap_ (defined below) between the
  local times in his city and the i-th person's city was D_i hours. The time gap
  between two cities is defined as follows. For two cities A and B, if the local
  time in city B is d o'clock at the moment when the local time in city A is 0
  o'clock, then the time gap between these two cities is defined to be
  min(d,24-d) hours. Here, we are using 24-hour notation. That is, the local
  time in the i-th person's city is either d o'clock or 24-d o'clock at the
  moment when the local time in Takahashi's city is 0 o'clock, for example.
  
  Then, for each pair of two people chosen from the N+1 people, he wrote out the
  time gap between their cities. Let the smallest time gap among them be s
  hours.
  
  Find the maximum possible value of s.
samples: [{"input": "3\n    7 12 8", "output": "4\n    \n\nFor example, consider the situation where it is 7, 12 and 16 o'clock in each\nperson's city at the moment when it is 0 o'clock in Takahashi's city. In this\ncase, the time gap between the second and third persons' cities is 4 hours.\n\n* * *"}, {"input": "2\n    11 11", "output": "2\n    \n\n* * *"}, {"input": "1\n    0", "output": "0\n    \n\nNote that Takahashi himself is also a participant."}]