#include <iostream>
#include <vector>
 
using namespace std;
 
int main()
{
    ios_base::sync_with_stdio(0);
    int d, k ,n, x, maks, xd; char c;
    cin >> d;
    while (d--)
    {
        cin >> n >> k;
        vector <int> y;
        y.push_back(1);
        x=maks=0;
 
        for (int i=0; i<n; i++)
        {
            cin >> c;
            if(c=='1') {x++; y.push_back(1);}
            else y[x]++;
        }
 
        if (y.size()==1) cout << n << endl;
        else
        {
        xd=0;
            for (int j=0; j<=k; j++) xd+=y[j];
                maks=xd;
            for (int i=k; i<y.size()-1; i++)
                {
                    xd+=y[i+1]; xd-=y[i-k];
                    if(xd>maks) maks=xd;
                }
        cout << maks-1 << endl;
        }
    }
    return 0;
}
 

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8
10 1
0101000001
12 2
010110101001
15 3
101000011100100
10 0
0000000000
10 1
0000000000
10 3
0010101000
10 4
0010101000
10 3
0101010101