#include <bits/stdc++.h>
using namespace std;
long long t, n, x, b[200005] = {0}, ans, ta, kk, kkk, ttt = 0;
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  string s;
  cin >> t;
  for (int jjj = 0; jjj < t; jjj++) {
    ta = 0;
    ans = 0;
    kk = 0;
    kkk = 0;
    cin >> n >> x;
    if (x == 0) {
      ta = 1;
    }
    for (int i = 0; i <= 2 * n; i++) {
      b[i] = 0;
    }
    cin >> s;
    for (int i = 0; i < n; i++) {
      if (s[i] == '0') {
        ans++;
        b[ans + n]++;
      } else {
        ans--;
        b[ans + n]++;
      }
    }
    if (ans == 0) {
      if (x <= n && x >= -n) {
        if (b[x + n] != 0) {
          cout << -1 << endl;
        } else {
          cout << ta << endl;
        }
      } else {
        cout << ta << endl;
      }
    } else {
      if (ans > 0) {
        kk = (x + n) / ans;
        kkk = (x - n - 1) / ans + 1;
        if (x <= n) {
          kkk = 0;
        }
        for (int i = kkk; i <= kk + 1; i++) {
          if (x - i * ans + n >= 0 && x - i * ans + n <= 2 * n) {
            ta = ta + b[x - i * ans + n];
          }
        }
        cout << ta << endl;
      }
      if (ans < 0) {
        kk = (n + x) / ans;
        kkk = (x - n) / ans;
        for (int i = max(kk - 1, ttt); i <= kkk + 1; i++) {
          if (x - i * ans + n >= 0 && x - i * ans + n <= 2 * n) {
            ta = ta + b[x - i * ans + n];
          }
        }
        cout << ta << endl;
      }
    }
  }
}
