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

#define int long long
//typedef pair<int, int> P;
#define mod 1000000007
#define INF (1LL<<60)
 
#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define YES puts("YES")
#define Yes puts("Yes")
#define NO  puts("NO")
#define No  puts("No")
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
 
const int dx[4] = { 1, 0, -1, 0 };
const int dy[4] = { 0, 1, 0, -1 };
 
 
#if 1
//-------------
// DUMPマクロ
// https://www.creativ.xyz/dump-cpp-652/
 
// vector
template <typename T>
istream& operator>>(istream& is, vector<T>& vec) {
    for (T& x : vec) is >> x;
    return is;
}
// pair
template <typename T, typename U>
ostream& operator<<(ostream& os, pair<T, U>& pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}
// vector
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
    os << "{";
    for (int i = 0; i < vec.size(); i++) {
        os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
    }
    os << "}";
    return os;
}
// map
template <typename T, typename U>
ostream& operator<<(ostream& os, map<T, U>& map_var) {
    os << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
// set
template <typename T>
ostream& operator<<(ostream& os, set<T>& set_var) {
    os << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
 
#define DUMPOUT cerr
 
void dump_func() {
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head&& head, Tail&& ... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) {
        DUMPOUT << ", ";
    }
    dump_func(std::move(tail)...);
}
#ifdef DEBUG
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
#endif

// res[i][c] := i 文字目以降で最初に文字 c が登場する index (存在しないときは n)
vector<vector<int> > calcNext(const string &S) {
    int n = (int)S.size();
    vector<vector<int> > res(n+1, vector<int>(26, n));
    for (int i = n-1; i >= 0; --i) {
        for (int j = 0; j < 26; ++j) res[i][j] = res[i+1][j];
        res[i][S[i]-'a'] = i+1;
    }
    return res;
}

signed main() {

    string s, t;
    cin >> s >> t;
    int N = s.size();
    string ss = s+s;
    int NN = ss.size();
    
    vector<vector<int>> v = calcNext(ss);
    
    int now=0, prev_idx = 0;
    int next_idx;
    rep(i,t.size()){
        next_idx = v[prev_idx][t[i]-'a'];
        dump(t[i],next_idx, prev_idx);
        if(next_idx==NN){ cout << -1 << endl; return 0;}
        now += next_idx - prev_idx;
        prev_idx = next_idx%N;
    }
    cout << now << endl;
    
    
}



Measured memory_bytes: 49152