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 collections
  
  n = int(input())
  
  inp_list = list(map(int, input().split()))
  inp_list.append(0)
  
  c = collections.Counter(inp_list)
  a = c.most_common()
  
  
  def ura(time):
      if time == 12:
          time = 12
      elif time == 0:
          time = 0
      else:
          time = 24 - time
  
      return time
  
  
  member = []
  
  for tup in a:
      if tup[1] > 1:
          member.append(tup[0])
          member.append(tup[0])
      elif tup[1] == 1:
          member.append(tup[0])
  
  
  ans = 0
  
  for i in range(2 ** len(member)):
      trry = format(i, "0" + str(len(member)) + "b")
      time_diff = 24
  
      for ii in range(len(member) - 1):
          for iii in range(ii + 1, len(member)):
              A = member[ii]
              if trry[iii] == "0":
                  B = member[iii]
              else:
                  B = ura(member[iii])
              a_b = abs(A - B)
              b_a = min(A, B) + 24 - max(A, B)
              time_diff = min(time_diff, a_b, b_a)
  
      ans = max(ans, time_diff)
  
  print(ans)
  
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."}]