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)

from collections import deque

def main():
    n,k = map(int,input().split())
    raw_list = input()
    
    q = deque([])

    startfeet = 0
    endfeet = 0
    max_len = 0
    for i in range(n):
        item = raw_list[i]
        if item == '0':
            endfeet = get_endhand(raw_list,i+1,n)
            append_list = [startfeet,endfeet]
            startfeet = get_startfeet(raw_list,i+1,n)

            if len(q) == k:
                if q[k-1][1] - q[0][0] + 1 > max_len:
                    max_len = q[k-1][1] - q[0][0] + 1
                q.popleft()
                q.append(append_list)

            else:
                q.append(append_list)
    print(max_len)

def get_startfeet(raw_list,i,n):
    for index in range(i,n):
        if raw_list[index-1] == '0' and raw_list[index] == '1':
            return index
    return index

def get_endhand(raw_list,i,n):
    for index in range(i,n):
        if raw_list[index-1] == '1' and raw_list[index] == '0':
            return index-1
    return index

if __name__ == "__main__":
    main()