#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 5;

string s, t;

int main() {
    // freopen("a.in", "r", stdin);
    // freopen("a.out", "w", stdout);
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> s >> t;
    if (t == "0" || t == "1") {
        for (char c : s) {
            if (c == t[0]) {
                cout << "-1\n";
                return 0;
            }
        }
        cout << "0\n";
    }
    if (t == "00" || t == "11") {
        int k = t[0] - '0', ans = 0, cnt = 0, c[2] = {};
        for (int i = 0; i < s.size(); i++) {
            if (i && s[i] != s[i - 1]) {
                c[s[i - 1] - '0'] += cnt;
                if (s[i - 1] == t[0]) {
                    ans += cnt - 1;
                }
                cnt = 0;
            }
            cnt++;
        }
        c[s.back() - '0'] += cnt;
        if (s.back() == t[0]) {
            ans += cnt - 1;
        }
        if (c[k] <= c[k ^ 1] + 1) {
            cout << ans << '\n';
        }
        else {
            cout << "-1\n";
        }
    }
    if (t == "01" || t == "10") {
        int ans = 0;
        for (int i = 1; i < s.size(); i++) {
            if (s[i - 1] == t[0] && s[i] == t[1]) {
                ans++;
            }
        }
        cout << ans << '\n';
    }
    if (t == "000" || t == "111") {
        int k = t[0] - '0', n = 0, cnt = 0, c[2] = {0}, a[N] = {0};
        for (int i = 0; i < s.size(); i++) {
            cnt++;
            if (i == s.size() - 1 || s[i] != s[i + 1]) {
                c[s[i] - '0'] += cnt;
                if (s[i] == t[0]) {
                    a[++n] = cnt;
                }
                cnt = 0;
            }
        }
        if ((c[k] - 1) / 2 > c[k ^ 1]) {
            cout << "-1\n";
        }
        else {
            int ans1 = 0, ans2 = 0;
            for (int i = 1; i <= n; i++) {
                if (a[i] == 1) {
                    continue;
                }
                if (a[i] & 1) {
                    ans2++;
                }
                ans1 += a[i] / 2 - 1;
            }
            while (c[k ^ 1] - n + 1 < ans1) {
                ans2++;
                n--;
            }
            cout << ans1 + ans2 << '\n';
        }
    }
    if (t == "010" || t == "101" || t == "001" || t == "011" || t == "100" || t == "110") {
        int ans = 0;
        for (int i = 2; i < s.size(); i++) {
            if (s[i - 2] == t[0] && s[i - 1] == t[1] && s[i] == t[2]) {
                ans++;
            }
        }
        if (t == "010" || t == "101") {
            ans = (ans - 1) / 2 + 1;
        }
        cout << ans << '\n';
    }

    return 0;
}