#include <iostream>
#include <vector>

using namespace std;

int maxConsecutiveOnes(vector<int>&array, int k)
{
    int left = 0, right = 0;

    int bestWindow = 0;
    int zeroCount = 0;
    while(right < array.size())
    {
        if(zeroCount <= k)
        {
            if(array[right] == 0)
                zeroCount++;

            right++;
        }

        if(zeroCount > k)
        {
            if(array[left] == 0)
                zeroCount--;

            left++;
        }

        if(zeroCount <= k && bestWindow < right-left)
            bestWindow = right-left;
    }

    return bestWindow;
}

int main()
{
    int n, k;
    cin >> n >> k;

    vector<int>array(n);
    for(int i = 0; i < n; i++)
        cin >> array[i];

    cout << maxConsecutiveOnes(array, k) << endl;
    return 0;
}