output_description: Print the maximum integer K such that we can turn all the characters of S into
  `0` by repeating the operation some number of times.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      S
attempt: def main():
      s = input()
  
      max_k = 0
  
  
      #バラバラ
      slist = []
      for i in range(len(s)):
          slist.append(s[i:i+1])
  
      for k in range(len(slist)):
          judge = testmethod(slist, k)
          if judge == 0:
              max_k = k
          
      print(max_k)
  
  def testmethod(list, k):
      
      for i in range(0, len(list) - k):
          target = list[i:i+k]
  
          for t2 in range(len(target)):
              if target[t2] == '0':
                  target[t2] = '1'
              else:
                  target[t2] = '0'
          list[i:i+k] = target
      
      for t in range(len(list)):
          if list[t] == '1'
              return 1
      
      return 0
  
problem_description: Statement
  
  You are given a string S consisting of `0` and `1`. Find the maximum integer K
  not greater than |S| such that we can turn all the characters of S into `0` by
  repeating the following operation some number of times.
  
    * Choose a contiguous segment [l,r] in S whose length is at least K (that is, r-l+1\geq K must be satisfied). For each integer i such that l\leq i\leq r, do the following: if S_i is `0`, replace it with `1`; if S_i is `1`, replace it with `0`.
samples: [{"input": "010", "output": "2\n    \n\nWe can turn all the characters of S into `0` by the following operations:\n\n  * Perform the operation on the segment S[1,3] with length 3. S is now `101`.\n  * Perform the operation on the segment S[1,2] with length 2. S is now `011`.\n  * Perform the operation on the segment S[2,3] with length 2. S is now `000`.\n\n* * *"}, {"input": "100000000", "output": "8\n    \n\n* * *"}, {"input": "00001111", "output": "4"}]