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: Wrong Answer)

N, K = map(int, input().split())
S = input()


status = S[0]
temp = 0
values = []

for i in range(N):
    if S[i] == status:
        temp += 1
    else:
        if status == '1':
            temp *= -1
        values.append(temp)
        status = S[i]
        temp = 1

if status == '1':
    temp *= -1
values.append(temp)

if len(values) == 1:
    if values[0] < 0:
        print(abs(values[0]))
    elif K >= 1:
        print(abs(values[0]))
    exit()

ans = 0

for i in range(len(values)):
    temp = 0
    renzoku = 0

    if values[i] < 0:
        renzoku = (2 * K + 1)
    else:
        renzoku = 2 * K

    if i + renzoku > len(values):
        break

    for x in range(renzoku):
        temp += abs(values[i + x])

    ans = max(ans, temp)

print(ans)