#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