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: S=input()
  l=len(S)
  if l%2==1:
      m=S[l//2]
      c=1
      for i in range l//2:
          if S[l//2-i-1]==m and S[l//2+i+1]==m:
              c+=2
          else:
              break
      ans=c+(l-c)//2
  else:
      m1=S[l//2-1]
      m2=S[l//2]
      c=0
      if m1==m2:
          c=2
          for i in range l//2-1:
          if S[l//2-i-2]==m1 and S[l//2+i+1]==m1:
              c+=2
          else:
              break
      ans=c+(l-c)//2
  print(ans)
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"}]