Problem:
Score : 400 points

Problem 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.

Constraints

N is an integer satisfying 1 \leq N \leq 10^5.

K is an integer satisfying 1 \leq K \leq 10^5.

The length of the string S is N.

Each character of the string S is 0 or 1.

Input

Input is given from Standard Input in the following format:

N K
S

Output

Print the maximum possible number of consecutive people standing on hands after at most K directions.

Sample Input 1

5 1
00010

Sample Output 1

4

We can have four consecutive people standing on hands, which is the maximum result, by giving the following direction:

Give the direction with l = 1, r = 3, which flips the first, second and third persons from the left.

Sample Input 2

14 2
11101010110011

Sample Output 2

8

Sample Input 3

1 1
1

Sample Output 3

1

No directions are necessary.

Solution in Python (3.4.3) (judge verdict: Runtime Error)

N, K = map(int,input().split())
S = list(map(int,input().strip()))
cur = S[0]
tmp = [] if cur == 1 else [0]
count = 1
def ngram(x,n):
  return [x[i:i+n] for i in range(0,len(x) - n + 1)]

for s in S[1:]:
  if s != cur:
    tmp.append(count)
    cur = s
    count = 0
  count += 1

tmp.append(count)
if cur == 0:
  tmp.append(0)
  
if len(tmp) == 1:
  print(tmp[0])
else:
  odd = tmp[::2]
  even = tmp[1::2]
  print(max([sum(a) + sum(b) for a,b in zip(ngram(odd,K+1),ngram(even,K))]))