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: #n>=25なら鳩ノ巣で0
  #2人以上居るdは一意
  #あとはしらみつぶし
  
  n = int(input())
  if n>=25:
      print(0)
      exit()
  
  d = list(map(int, input().split( )))
  if 0 in d:##
      print(0)
      exit()
  d.append(0)
  dic = {}
  
  for di in d:
      if di in dic:
          dic[di] += 1
      else:
          dic[di]= 1
  solo = []
  times = []
  for di in dic:
      if dic[di]==1:#di=0はここに入る
          solo.append(di)
      elif dic[di]==2:
          times.append(di)
          if di!=12:
              times.append(24-di)
          else:
              print(0):
                  exit()
      else:
          print(0)
          exit()
          
  ans = 0
  m = len(solo)
  bit = 1<<m
  
  for i in range(bit):
      times2 = []
      for t in times:
          times2.append(t)
      for j in range(m):
          if i>>j&1:
              times2.append(solo[j])
          elif solo[j]:
              times2.append(24-solo[j])
      times2.sort()
      dif = 24
      if len(times2)==1:###
          print(0)
          exit()
      #print(times2)
  
      for k in range(len(times2)-1):
          dif = min(dif,times2[k+1]-times2[k])
      dif = min(dif,times2[0] + 24 - times2[-1])
      ans = max(ans,dif)
  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."}]