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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main(){
  int n,m,d[100010],l=0,r=0,i,c=0,a=0;
  scanf("%d %d",&n,&m);
  for(i=0;i<n;i++)scanf("%1d",&d[i]);
  if(d[0]==0)c=1;
  for(l=0;l<n;l++){
    while(c<m+1){
      if(d[r]==1&&d[r+1]==0)c++;
      if(r==n)goto END;
      r++;
    }//printf("%d %d\n",l,r);
    if(a<r-l)a=r-l;
    if(d[l]==0&&d[l+1]==1)c--;
  }//printf("%d %d\n",l,r);
 END:;//printf("%d %d\n",l,r);
  if(a<r-l)a=l-r;
  printf("%d\n",a);
  return 0;
}