#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define FILL(a, b) memset(a, b, sizeof(a))

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;


void solve(){
	int n, k;
	string s;
	cin >> n >> k >> s;
	
	int l = 0, r = n;
	while(r - l > 1){
		int m = (l + r) / 2;
		
		int cnt = 0;
		int last = -m;
		FOR(i, 0, n){
			if(s[i] == '0')
				continue;
			if(i - last < m)
				continue;
			cnt++;
			last = i;
		}
		
		
		
		if(cnt <= k)
			r = m;
		else
			l = m;
	}
	cout << r << "\n";
}


int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int t;
	cin >> t;
	while(t--)
		solve();
	
	
	return 0;
}