#include<iostream>
#include<vector>
#include<cmath>
using namespace std;
int t;
int main(){
    cin >> t;
    while (t--){
        int n, x; cin >> n >> x;
        string s; cin >> s; s += s[0];
        vector<int> b(2*n); b[0] = ((s[0] == '1') ? -1 : 1);
        for (int i = 1; i < n + 1; ++i)
            b[i] = b[i-1] + ((s[i] == '1') ? -1 : 1);
        int ch = b[n] - b[0];
        int c = 0;
        for (int i = 0; i < n; ++i){
            if (ch != 0) {
                    if ((ch > 0) && (x - b[i] >= 0) && ((x - b[i]) % ch == 0)) c++;
                    else if ((ch < 0) && (x - b[i] <= 0)) if ((b[i] - x) % ((-1)*ch) == 0) c++;
            }
            else if (b[i] == x){
                c = -1;
                cout << c << endl;
                break;
            }
        }
        if (x == 0 && c != -1) c++;
        if (c != -1)
            cout << c << endl;
    }
}