#include <bits/stdc++.h>
using namespace std;
const double PI = 2 * acos(0.0);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());
const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";
template <class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
  return out << "{" << a.first << ", " << a.second << "}";
}
template <class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << "}";
}
template <class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << ", " << get<3>(a) << "}";
}
template <class T>
inline ostream &operator<<(ostream &out, vector<T> &a) {
  out << "[";
  for (long long i = 0; i < (long long)(a.size()); ++i)
    out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
  return out;
}
void smain();
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << setprecision(10) << fixed;
  smain();
  return 0;
}
void smain() {
  long long t;
  cin >> t;
  while (t--) {
    long long n, k;
    string s;
    cin >> n >> k >> s;
    vector<long long> p(2);
    map<long long, long long> mp;
    for (long long i = 0; i < s.size(); i++) {
      p[s[i] - '0']++;
      long long u = p[0] - p[1];
      mp[u]++;
    }
    long long v = p[0] - p[1];
    if (v == 0) {
      if (mp[k] != 0) {
        cout << -1 << "\n";
      } else {
        cout << mp[k] << "\n";
      }
      continue;
    }
    long long sum = 0;
    for (auto h : mp) {
      if ((k - h.first) % abs(v) == 0 && (k - h.first) / v >= 0) {
        sum += h.second;
      }
    }
    if (k == 0) sum++;
    cout << sum << "\n";
  }
}
