#include <bits/stdc++.h>

using namespace std;

int balanceIncrement(const string &s)
{
    int balance = 0;
    for(char c : s)
    {
        if(c == '0')
            balance++;
        if(c == '1')
            balance--;
    }
    return balance;
}

int main()
{
    cin.tie();
    ios::sync_with_stdio(false);

    int t;
    string s;
    cin >> t;
    while(t--)
    {
        int n, x;
        cin >> n >> x;
        cin >> s;

        int inc = balanceIncrement(s);
        if(inc == 0)
            inc = 1e9;
        int sol = 0;
        int balance = 0;
        for(char c : s)
        {
            if(c == '0')
                balance++;
            if(c == '1')
                balance--;

            if(inc > 1 && (x - balance) % abs(inc) == 0)
                sol++;
            else if(inc < -1 && (balance - x) % abs(inc) == 0)
                sol++;
            else if(inc == 1 && balance <= x)
                sol++;
            else if(inc == -1 && balance >= x)
                sol++;

        }

        if(inc == 1e9 && x == 0)
            sol = -1;
        else if(x == 0)
            sol++;
        cout << sol << '\n';
    }

    return 0;
}