output_description: Print the maximum possible number of consecutive people standing on hands
  after at most K directions.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
      S
attempt:     N, K = map(int, input().split())
      S = list(map(int, input()))
       
      Z = [j for j, s in enumerate(S) if (j > 0 and s == 0 and S[j] != S[j-1]) or (j == 0 and s == 0)] + [N]
      Y = [j for j, s in enumerate(S) if (j > 0 and s == 1 and S[j] != S[j-1]) or (j == 0 and s == 1)]
      result = 0
      if len(Z) <= K:
          print(N)
      else:
          for i in range(len(Z)-K):
              if i == 0:
                  result = Z[i+K]
              else:
                  result = max(result, Z[i+K] - Y[i if Y[0] < Z[0] else i-1])
          print(result)
problem_description: Statement
  
  N people are arranged in a row from left to right.
  
  You are given a string S of length N consisting of `0` and `1`, and a positive
  integer K.
  
  The i-th person from the left is standing on feet if the i-th character of S
  is `0`, and standing on hands if that character is `1`.
  
  You will give the following direction at most K times (possibly zero):
  
  **Direction** : Choose integers l and r satisfying 1 \leq l \leq r \leq N, and
  flip the l-th, (l+1)-th, ..., and r-th persons. That is, for each i = l, l+1,
  ..., r, the i-th person from the left now stands on hands if he/she was
  standing on feet, and stands on feet if he/she was standing on hands.
  
  Find the maximum possible number of **consecutive** people standing on hands
  after at most K directions.
samples: [{"input": "5 1\n    00010", "output": "4\n    \n\nWe can have four consecutive people standing on hands, which is the maximum\nresult, by giving the following direction:\n\n  * Give the direction with l = 1, r = 3, which flips the first, second and third persons from the left.\n\n* * *"}, {"input": "14 2\n    11101010110011", "output": "8\n    \n\n* * *"}, {"input": "1 1\n    1", "output": "1\n    \n\nNo directions are necessary."}]