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 PyPy3 (2.4.0) (judge verdict: Runtime Error)

import sys
input = sys.stdin.readline()

'''
allinputs = iter(input().splitlines())
input = lambda : next(allinputs)
#'''

N, K = map(int, input().split())
S = list(input())
S = [int(i) for i in S]

L = [0]
R = [0]

for i in range(N):
	if S[i] == 0:
		if i == N - 1:
			L.append(i + 1)
		elif S[i + 1] == 1:
			L.append(i + 1)
	if S[N - i -1] == 0:
		if i == N - 1:
			R.append(i + 1)
		elif S[N - i -2] == 1:
			R.append(i + 1)

ans = 0
M = len(L) - K

if M <= 0:
	ans = N
	
for i in range(M):
	tmp = N - L[i] - R[M - i - 1]
	if tmp > ans:
		ans = tmp

print(ans)