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())
w=input()
l=[]
c=0
w="1"+w
for i in range(1,1+n):
  if w[i]!=w[i-1]:
    l.append(c)
    c=1
  else:
    c+=1
l.append(c)
if w[-1]=="0":
  l.append(0)
s=l[0]
for i in range(1,1+k):
  s+=l[2*i]+l[2*i-1]
s1=s
c1=l[0]+l[1]
for i in range(1,(len(l)+1)/2):
  s1=s1-l[2*i-2]-l[2*i-1]+l[2*i-2+2*k+1]+l[2*i+2*k]
  if s1>s:
    s=s1
print(s)