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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;

namespace ABC124D
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Split(' ').ToArray();
            var line1 = Console.ReadLine().ToArray();

            var N = int.Parse(line[0]); var K = int.Parse(line[1]);

            int[] set = new int[N];
            int[] setdig = new int[N];
            int j = 0;

            for(var i = 0; i < N; i++)
            {
                set[i] = 1;
            }

            if(N == 1)
            {
                Console.WriteLine(1);
            }
            else
            {
                for(var i = 1; i < N; i++)
                {
                    if(line1[i-1] == '1')
                    {
                        setdig[j] = 1;
                    }

                    if(line1[i-1] == line1[i])
                    {
                        set[j]++;
                    }
                    else
                    {
                        j++;
                    }
                }

                int setlen = j + 1;

                int maxlen = 0;

                for(var i = 0; i < setlen - 2 * K; i++)
                {
                    int total = 0;

                    if(setdig[i] == 0)
                    {
                        for(var l = 0; l < 2 * K; l++)
                        {
                            total += set[i + l];
                        }
                    }
                    else
                    {
                        for(var l = 0; l < 2 * K + 1; l++)
                        {
                            total += set[i + l];
                        }
                    }

                    if(maxlen < total)
                    {
                        maxlen = total;
                    }
                }

                Console.WriteLine(maxlen);
            }
        }
    }
}