#include <bits/stdc++.h>
#define range(i, l, r) for(int (i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (int (i) = (r) - 1; (i) >= l; (i)--)
using namespace std;
template <typename T>
using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

template <typename S, typename T>
ostream& operator <<(ostream& os, pair<S, T> p) {
    os << "(";
    os << p.first << ", " << p.second;
    return os << ")";
}

template <typename T>
ostream& operator <<(ostream& os, vec<T> v) {
    os << "[";
    if (v.size() == 0) return os << "]";
    for (int i = 0; i < v.size() - 1; i++) {
        os << v.at(i) << ", ";
    }
    return os << v.at(v.size() - 1) << "]";
}

template <typename T>
ostream& operator <<(ostream& os, set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename T>
ostream& operator <<(ostream& os, unordered_set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    cout << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        cout << ", " << *it;
    }
    return cout << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, unordered_map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    cout << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        cout << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

lint pow(lint num, lint e, lint MOD) {
    lint res = 1;
    lint cur_num = num;
    while (e) {
        if (e & 1) {
            res *= cur_num;
            res %= MOD;
        }
        cur_num *= cur_num;
        cur_num %= MOD;
        e >>= 1;
    }
    return res;
}

int main() {
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    string s, t;
    cin >> s >> t;
    // if t has a character that doesn't exist in s, it's impossible.
    unordered_set<char> chars_in_s;
    for (const auto& c : s) chars_in_s.emplace(c);
    for (const auto& c : t) {
        if (!chars_in_s.count(c)) {
            cout << -1 << "\n";
            return 0;
        }
    }
    // double s
    lint len_s = s.size();
    string s_double(s);
    for (const auto c : s) s_double.push_back(c);

    // cout << s << "\n";
    // create a mapping
    unordered_map<char, vec<lint>> indices;
    range(i, 0, s_double.size()) {
        char c = s_double.at(i);
        if (!indices.count(c)) {
            indices.emplace(c, vec<lint>(1, i));
        }
        else indices.at(c).emplace_back(i);
    }

    // cout << "hoge" << "\n";
    // cout << indices << "\n";
    // iterate through t, checking the closest corresponding character.
    // (cur_idx_s
    lint cur_idx_s = -1, pos_from_start = 0;
    for (const auto& c : t) {
        auto it_idx = upper_bound(indices.at(c).begin(), indices.at(c).end(), cur_idx_s);
        if (it_idx == indices.at(c).end()) {
            cout << "hogehoge" << "\n";
            return 0;
        }
        lint idx = *it_idx;
        pos_from_start += idx - cur_idx_s;
        // cout << cur_idx_s << " " << idx << "\n";
        cur_idx_s = idx;
        if (cur_idx_s >= len_s) cur_idx_s -= len_s;
    }
    cout << pos_from_start << "\n";
}


Measured memory_bytes: 2884