#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';
    } else if (m == 2) {
        if (t[0] != t[1]) {
            int till = n - (find(s.rbegin(), s.rend(), '1') - s.rbegin());
            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 {
            int cnt = count(s.begin(), s.end(), '1');
            if (cnt * 2 + 1 < n) {
                cout << "-1\n";
            } else {
                int ans = 0;
                for (int i = 0, j = 0; i < n; i = j) {
                    while (j < n && s[i] == s[j]) {
                        j += 1;
                    }
                    if (s[i] == '0') {
                        ans += j - i - 1;
                    }
                }
                cout << ans << '\n';
            }
        }
    } else {
        if (s.find(t) == string::npos) {
            cout << "0\n";
            return 0;
        }
        if (t == "001") {
            char x = '0' ^ '1';
            for (char &c : s) {
                c ^= x;
            }
            for (char &c : t) {
                c ^= x;
            }
            reverse(s.begin(), s.end());
            reverse(t.begin(), t.end());
        }
        if (t == "011") {
            int ans = 0;
            vector<bool> a(n);
            for (int i = 0; i < n; ++i) {
                if (s[i] == '0' || (i > 0 && s[i - 1] == '0')) {
                    a[i] = true;
                }
            }
            int la = n - (find(a.rbegin(), a.rend(), false) - a.rbegin());
            for (int i = 0; i < la - 1; ++i) {
                if (a[i] != a[i + 1] && a[i]) {
                    ans += 1;
                }
            }
            cout << ans << '\n';
        } else if (t == "000") {
            int cnt = count(s.begin(), s.end(), '1');
            if (cnt * 3 + 2 < n) {
                cout << "-1\n";
            } else {
                int ans = 0, cnt10 = 0;
                for (int i = 0; i + 1 < n; ++i) {
                    if (s[i] == '0' && s[i + 1] == '1' && (i + 2 == n || s[i + 2] == '0')){
                        cnt10 += 1;
                    }
                }
                for (int i = 0, j = 0; i < n; i = j) {
                    while (j < n && s[i] == s[j]) {
                        j += 1;
                    }
                    if (s[i] == '0') {
                        ans += (j - i - 1) / 2;
                    }
                }
                int c = cnt - cnt10;
                int need = max(0, (n - cnt - c * 2 - 2) / 2);
                cout << ans + (need + 1) / 2 << '\n';
            }
        } else if (t == "010") {
            int ans = 0;
            for (int i = 1; i < n - 1; ++i) {
                if (s[i] == '1' && s[i - 1] == s[i + 1] && s[i - 1] == '0') {
                    ans += 1;
                }
            }
            cout << (ans + 1) / 2 << '\n';
        } else {
            assert(false);
        }
    }

    return 0;
}