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 Ruby (2.3.3) (judge verdict: Runtime Error)

n,k = $stdin.gets.split.map(&:to_i)
s = $stdin.gets.chomp.split("").map(&:to_i)
ichi = s[0]
ary=[]
result = []
now = s[0]
count = 0
 
n.times do |i|
  if now != s[i]
    ary.push(count)
    count = 0
  end
  count += 1
  now = s[i]
end
 
ary.push(count)
 
if ichi == 0
  sum = 0
  (k*2).times do |i|
	if !ary[i].nil?
      sum += ary[i]
    end
  end
  result.push(sum)
end
 
ary.size.times do |i|
  if i == 0
    sum = 0
    i = i * 2 + 1 - ichi
    (k*2+1).times do |j|
      if !ary[i+j].nil?
        sum += ary[i+j]
      else
        break
      end
    end
    result.push(sum)
    now = sum
  else
    i = i * 2 + 1 - ichi
    now -= ary[i-2] + ary[i-1]
    if !ary[i+k*2].nil?
      now += ary[i+k*2] + ary[i+k*2-1]
    else
      if !ary[i+k*2-1].nil?
        ary += ary[i+k*2-1]
      end
      break
    end
    result.push(now)
  end
end
 
puts result.max