#include <bits/stdc++.h>
// #pragma GCC optimize(3, "Ofast", "inline")
// #include <ext/pb_ds/tree_policy.hpp>
// #include <ext/pb_ds/assoc_container.hpp>
// using namespace __gnu_pbds;
// tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> s;
using i64 = long long;
using u32 = unsigned int;
using u64 = unsigned long long;
using i128 = __int128_t;
using namespace std;
const int N = 1e5 + 5;
// const int B = 3e6;
// const int M = 2e6 + 5;
// const int base = 13131;
// const int base = 17171;
// const int mod = 998244353;
// const int mod = 1e9 + 7;
// const i64 mod = 1000000000000000003LL;
// const double pi = acos(-1);
// mt19937 rnd(chrono::duration_cast<chrono::nanoseconds>(chrono::system_clock::now().time_since_epoch()).count());

template <int mod>
unsigned int down(unsigned int x)
{
    return x >= mod ? x - mod : x;
}
template <int mod>
struct Modint
{
    unsigned int x;
    Modint() = default;
    Modint(unsigned int x) : x(x) {}
    friend istream &operator>>(istream &in, Modint &a) { return in >> a.x; }
    friend ostream &operator<<(ostream &out, Modint a) { return out << a.x; }
    friend Modint operator+(Modint a, Modint b) { return down<mod>(a.x + b.x); }
    friend Modint operator-(Modint a, Modint b) { return down<mod>(a.x - b.x + mod); }
    friend Modint operator*(Modint a, Modint b) { return 1ULL * a.x * b.x % mod; }
    friend Modint operator/(Modint a, Modint b) { return a * ~b; }
    friend Modint operator^(Modint a, int b)
    {
        Modint ans = 1;
        for (; b; b >>= 1, a *= a)
            if (b & 1)
                ans *= a;
        return ans;
    }
    friend Modint operator~(Modint a) { return a ^ (mod - 2); }
    friend Modint operator-(Modint a) { return down<mod>(mod - a.x); }
    friend Modint &operator+=(Modint &a, Modint b) { return a = a + b; }
    friend Modint &operator-=(Modint &a, Modint b) { return a = a - b; }
    friend Modint &operator*=(Modint &a, Modint b) { return a = a * b; }
    friend Modint &operator/=(Modint &a, Modint b) { return a = a / b; }
    friend Modint &operator^=(Modint &a, int b) { return a = a ^ b; }
    friend Modint &operator++(Modint &a) { return a += 1; }
    friend Modint operator++(Modint &a, int)
    {
        Modint x = a;
        a += 1;
        return x;
    }
    friend Modint &operator--(Modint &a) { return a -= 1; }
    friend Modint operator--(Modint &a, int)
    {
        Modint x = a;
        a -= 1;
        return x;
    }
    friend bool operator==(Modint a, Modint b) { return a.x == b.x; }
    friend bool operator!=(Modint a, Modint b) { return !(a == b); }
};
typedef Modint<998244353> mint;

void solve()
{
    string s, t;
    cin >> s >> t;
    int n = s.length(), m = t.length(), ans = 0;
    while (m)
    {
        vector<int> f(m);
        f[0] = -1;
        for (int i = 1, k = -1; i < m; i++)
        {
            while (k != -1 && t[k + 1] != t[i])
                k = f[k];
            if (t[k + 1] == t[i])
                k++;
            f[i] = k;
        }
        for (int i = 0, k = -1; i < n; i++)
        {
            while (k != -1 && t[k + 1] != s[i])
                k = f[k];
            if (t[k + 1] == s[i])
                k++;
            if (k == m - 1)
            {
                cout << ans << '\n';
                return;
            }
        }
        int p = -1;
        for (int i = 0; i < m; i++)
        {
            if (t[i] == 'a')
                continue;
            if (~p && i % 2 != p)
            {
                cout << -1 << '\n';
                return;
            }
            p = i % 2;
        }
        if (!~p)
            p = 1;
        string tmp;
        for (int i = p; i < m; i += 2)
            tmp.push_back(t[i]);
        if ((p & 1) == (m & 1))
            n = s.length() - 1;
        if (t == tmp)
        {
            cout << -1 << '\n';
            return;
        }
        t = tmp;
        m = t.length();
        ans++;
    }
    cout << ans << '\n';
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    // cin >> t;
    cout << fixed << setprecision(10);
    while (t--)
        solve();
}