#include <bits/stdc++.h>

using namespace std;
using ll = long long;

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

    string s, t;
    cin >> s >> t;

    const int n = size(s), m = size(t);

    if (t[0] == '1') {
        char x = '0' ^ '1';
        for (char &c : s) {
            c ^= x;
        }
        for (char &c : t) {
            c ^= x;
        }
    }

    if (m == 1) {
        cout << (s.find(t) == string::npos ? 0 : -1) << '\n';
        return 0;
    }
    
    if (m == 2) {
        if (t[0] != t[1]) {
            int till = find(s.begin(), s.end(), '1') - s.begin();
            if (till == n) {
                cout << 0 << '\n';
            } else {
                int ans = 0;
                for (int i = 0, j = 0; i < till; i = j) {
                    while (j < n && s[i] == s[j]) {
                        j += 1;
                    }
                    ans += s[i] == '0';
                }
                cout << ans << '\n';
            }
        } else {

        }
    }

    return 0;
}