#include <bits/stdc++.h>
#define REP(i, n)     for(int i = 0;i < n;i++)
#define REPR(i, n)    for(int i = n;i >= 0;i--)
#define FOR(i, m, n)  for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VRSORT(v) sort(v.begin(), v.end(),greater<int>());
#define ALL(X) (X).begin(),(X).end()
#define INF 99999999
#define M_PI 3.14159265358979323846
#define MOD 1000000007

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 0};
int dy[]={0, 1, 0, -1, 0};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) os << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }


string s,t;

void input(){
  #ifdef __LOCAL
      fs::path p = __FILE__;
      fs::path input,output;
      input = output = p.parent_path();
      input += string("/input/") + string(p.stem()) + string(".txt");
      output += string("/output/") + string(p.stem()) + string(".txt");
      freopen(input.c_str(), "r", stdin);
      freopen(output.c_str(), "w", stdout);
  #endif

  fast_io();
  cin >> s >> t;
}

map<char, vector<int> > t_position;

// yより大きいXの元のうち最小値を出力。
// 存在しない場合-1を出力
int __seek_min(vector<int> const& X, ll const& y){
  vector<int> Z;
  for(auto x:X) if(x>y) Z.push_back(x);
  if(Z.empty()) return -1;
  return *min_element(ALL(Z));
}

// バイナリサーチで基準yより大きい数の最小値を求める。
int seek_min(vector<int> const& X, ll const& y){
  if(y>=X.back()) return -1;
  auto itr = lower_bound(ALL(X),(y+1));
  // // Xにyより大きい数が存在しない場合。
  // if((X.end()-itr)==0) return -1;
  return *itr;
}

string A="abcdefghijklmnopqrstuvwxyz";

ll solve(){
  input();

  ll res=0LL;
  int halt=0;
  int halt_break=0;
  for(char a:t) halt_break+=(a+0);

  for(int i=0;i<t.size();i++){
    if(halt>=halt_break) break;
    if(!t_position[t[i]].empty()) continue;

    for(int j=0;j<s.size();j++){
      if(t[i]==s[j]) t_position[t[i]].push_back(j);
    }

    if(t_position[t[i]].empty()) return -1;
    halt += (t[i]+0);
  }
  ll j=-1;
  // 必要なsの個数をresで表す。
  for(int i=0;i<t.size();i++){
    // if(t_position[t[i]].empty()) return -1;
    j = seek_min(t_position[t[i]], j);
    if(j==-1) {
      res++;
      j = seek_min(t_position[t[i]], j);
    }
  }
  ll ans=0LL;
  ans = res*((ll)s.size())+j+1LL;
  return ans;
}

int main()
{
  cout << solve() << endl;
  return 0;
}


Measured memory_bytes: 1228