#include <bits/stdc++.h>
using namespace std;
vector<int> pri;
vector<int> path;
unsigned long long power(unsigned long long x, int y, int p) {
  unsigned long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
unsigned long long modInverse(unsigned long long n, int p) {
  return power(n, p - 2, p);
}
unsigned long long nCrModPFermat(unsigned long long n, int r, int p) {
  if (n < r) return 0;
  if (r == 0) return 1;
  unsigned long long fac[n + 1];
  fac[0] = 1;
  for (int i = 1; i <= n; i++) fac[i] = (fac[i - 1] * i) % p;
  return (fac[n] * modInverse(fac[r], p) % p * modInverse(fac[n - r], p) % p) %
         p;
}
long long pp(long long n, long long mod) {
  if (n == 0) return 1;
  long long ans1 = pp(n / 2, mod);
  ans1 = (ans1 * ans1) % mod;
  if (n % 2) ans1 = (ans1 * 2) % mod;
  return ans1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    long long n, x;
    cin >> n >> x;
    string s = "";
    cin >> s;
    unordered_map<int, int> mp;
    int sum = 0;
    for (int i = 0; i < n; i++) {
      sum += s[i] - '0';
      mp[i + 1 - (sum)-sum]++;
    }
    sum -= (n - sum);
    if (sum == 0) {
      if (x > n || x < -n) {
        cout << 0 << endl;
        continue;
      }
      if (mp.count(x)) {
        cout << -1 << endl;
        continue;
      }
      cout << 0 << endl;
      continue;
    }
    long long ans = 0;
    if (x == 0) ans++;
    if (sum > 0) {
      if (x < -1 * n) {
        int kk = -n - x;
        x = -n + sum - kk % sum - sum;
      }
      while (x <= n) {
        ans += mp[x];
        x += sum;
      }
    } else {
      if (x > n) {
        int ll = -1 * sum;
        int kk = x - n;
        x = n - (ll - kk % ll) + ll;
      }
      while (x >= -n) {
        ans += mp[x];
        x += sum;
      }
    }
    cout << ans << endl;
  }
}
