#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
// define
const int INF = 1 << 24;
#define endl "\n"
#ifdef LOCAL
#define lout cerr
#else
ostream devnull(0);
#define lout devnull
#endif
#define AMULET \
  cin.tie(0);  \
  ios::sync_with_stdio(false);
// Inspired by: https://github.com/kurokoji/.cpp-Template/blob/master/template/template2.cpp
#define GET_MACRO(_1, _2, _3, _4, NAME, ...) NAME
#define rep(...)                                 \
  GET_MACRO(__VA_ARGS__, rep4, rep3, rep2, rep1) \
  (__VA_ARGS__)
#define rep1(n) rep2(_, n)
#define rep2(i, n) rep3(i, 0, n)
#define rep3(i, a, n) rep4(i, a, n, 1)
#define rep4(i, a, n, d) rep5(i, a, n, d, <)
#define rep5(i, a, n, d, o) for (auto i = decltype(n)(a), _n = (n); i o _n; i += (d))

#define rrep(...)                                    \
  GET_MACRO(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1) \
  (__VA_ARGS__)
#define rrep1(a) rrep2(_, a)
#define rrep2(i, a) rrep3(i, a, 0)
#define rrep3(i, a, n) rrep4(i, a, n, -1)
#define rrep4(i, a, n, d) rep5(i, (a)-1, n, d, >=)

#define repc(...)                                    \
  GET_MACRO(__VA_ARGS__, repc4, repc3, repc2, repc1) \
  (__VA_ARGS__)
#define repc1(n) repc2(_, n)
#define repc2(i, n) repc3(i, 0, n)
#define repc3(i, a, n) repc4(i, a, n, 1)
#define repc4(i, a, n, d) rep5(i, a, n, d, <=)

#define dump(x) lout << #x << " = " << x << endl;
// alias
typedef long long ll;
typedef long long lint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
// func
template <class C>
inline void vcin(C &c);
template <class C, class D>
inline void vcin(C &c, D &d);
template <class C>
inline void vcout(const C &c, const string separate = "\n");
template <class T = int>
inline T in();
template <class T>
inline bool chmin(T &a, T b);
template <class T>
inline bool chmax(T &a, T b);
//http://beet-aizu.hatenablog.com/entry/2018/04/08/145516
template <typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...)); }

void solve()
{
  string s, t;
  cin >> s >> t;

  const int n = s.length();

  map<char, vector<int>> pos;

  rep(i, n)
  {
    pos[s[i]].push_back(i);
  }

  int last = 0, cnt = 0;
  for (char c : t)
  {
    const auto &p = pos[c];

    if (p.size() == 0)
    {
      cout << -1 << endl;
      return;
    }

    auto itr = lower_bound(p.begin(), p.end(), last);
    if (itr != p.end())
    {
      last = *itr;
    }
    else
    {
      last = p[0];
      cnt++;
    }
    last++;
  }

  cout << (1LL * cnt * n + last) << endl;
}

signed main()
{
  AMULET
  solve();
  return 0;
}

template <class C>
inline void vcin(C &c)
{
  for (auto &&a : c)
  {
    cin >> a;
  }
}

template <class C, class D>
inline void vcin(C &c, D &d)
{
  for (auto it1 = c.begin(), it2 = d.begin(); it1 != c.end() && it2 != d.end(); it1++, it2++)
  {
    cin >> *it1 >> *it2;
  }
}
template <class C>
inline void vcout(const C &c, const string separate)
{
  for (auto it = c.begin(); it != c.end(); it++)
  {
    if (it != c.begin())
      cout << separate;
    cout << *it;
  }
}
template <class T = int>
inline T in()
{
  T x;
  cin >> x;
  return (x);
}
template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}


Measured memory_bytes: 1228