//
//  main.cpp
//  test130
//
//  Created by  on 2019/06/16.
//  Copyright © 2 All rights reserved.
//
//
//  main.cpp
//  new
//
//  Created on 2019/06/09.
//  Copyright  All rights reserved.
//

// C++ includes used for precompiling -*- C++ -*-

// Copyright (C) 2003-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file stdc++.h
 *  This is an implementation file for a precompiled header.
 */

// 17.4.1.2 Headers

// C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif


#define f(i,n) for(int i=0;i<(n);i++)


#define inf (int)(3e18)
#define int long long
#define mod (int)(1000000007)

using namespace std;

//Library
//モッドパウ
int modpow(int x, int y, int m = mod) {
    int res = 1;
    while (y) {
        if (y % 2) {
            res *= x;
            res %= m;
        }
        x = x * x % mod;
        y /= 2;
    }
    return res;
}

int mypow(int x, int y) {
    int res = 1;
    while (y) {
        if (y % 2) {
            res *= x;
        }
        x = x * x ;
        y /= 2;
    }
    return res;
}
//is the number (x) a prime number?
bool prime(int x){
    for (int i=2; i*i<=x; i++) {
        if (!(x%i)) {
            return false;
        }
    }
    return true;
}

double kyori(pair<int, int> f, pair<int, int> s){
    double ans=0;
    double t = fabs(f.first-s.first);
    double y = fabs(f.second-s.second);
    ans=sqrt(t*t+y*y);
    return ans;
}

//saidai-kouyakusuu
int gcd(int x,int y){
    if (!y) {
        return x;
    }
    return gcd(y,x%y);
}

//Union-Find Tree

class Union_Find {
    vector<int> par;
    vector<int> rankmy;
public:
    Union_Find(int size){
        par = vector<int>(size);
        rankmy = vector<int>(size);
        for (int i=0; i<size; i++) {
            par[i]=i;
        }
    }
    
    int find(int x){
        if (par[x]==x) {
            return x;
        }
        return par[x]=find(par[x]);
    }

    void unite(int x,int y){
        x=find(x);
        y=find(y);
        if (x==y) {
            return;
        }
        if (rankmy[x]<rankmy[y]) {
            par[x]=y;
        }else{
            par[y]=x;
            if (rankmy[x]==rankmy[y]) {
                rankmy[x]++;
            }
        }
    }

    bool same(int x,int y){
        return find(x)==find(y);
    }
    
};

//Union-Find-End

//SegTree
template <class T>
class SegTree {
    int n;                       // 葉の数
    vector<T> data;              // データを格納するvector
    T def;                       // 初期値かつ単位元
    function<T(T, T)> operation; // 区間クエリで使う処理
    function<T(T, T)> update;    // 点更新で使う処理
 
    // 区間[a,b)の総和。ノードk=[l,r)に着目している。
    T _query(int a, int b, int k, int l, int r) {
        if (r <= a || b <= l) return def; // 交差しない
        if (a <= l && r <= b)
            return data[k]; // a,l,r,bの順で完全に含まれる
        else {
            T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2); // 左の子
            T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r); // 右の子
            return operation(c1, c2);
        }
    }
 
  public:
    // _n:必要サイズ, _def:初期値かつ単位元, _operation:クエリ関数,
    // _update:更新関数
    SegTree(size_t _n, T _def, function<T(T, T)> _operation,
            function<T(T, T)> _update)
        : def(_def), operation(_operation), update(_update) {
        n = 1;
        while (n < _n) {
            n *= 2;
        }
        data = vector<T>(2 * n - 1, def);
    }
 
    // 場所i(0-indexed)の値をxで更新
    void change(int i, T x) {
        i += n - 1;
        data[i] = update(data[i], x);
        while (i > 0) {
            i = (i - 1) / 2;
            data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
        }
    }
 
    // [a, b)の区間クエリを実行
    T query(int a, int b) {
        return _query(a, b, 0, 0, n);
    }
 
    // 添字でアクセス
    T operator[](int i) {
        return data[i + n - 1];
    }
};

#define R_MIN ([](long long a, long long b) { return min(a, b); })
#define R_MAX ([](long long a, long long b) { return max(a, b); })
#define R_SUM ([](long long a, long long b) { return a + b; })

#define NORMAL_UPDATE ([](long long a, long long b) { return b; })
#define ADD_UPDATE ([](long long a, long long b) { return a + b; })
#define MINUS_UPDATE ([](long long a, long long b) { return a - b; }
//Seg-Tree-End

//dfs
vector<int> v[100004];
bool went[100004];
void dfs(int x){
    went[x]=true;
    for (int i=0; i<v[x].size(); i++) {
        if (!went[v[x][i]]) {
            dfs(v[x][i]);
        }
    }
}

//number of keta
int keta(int x){
    int ans=0;
    while (x) {
        x/=10;
        ans++;
    }
    return ans;
}

//sum of keta
int ketasum(int x){
    int ans=0;
    while (x) {
        ans+=x%10;
        x/=10;
    }
    return ans;
}
//Library-End


int n,c,ans,now;
vector<int> aru[30];
string s,t;
bool ss[50],tt[50];
signed main(){
    cin>>s>>t;
    for (int i=0; i<s.size(); i++) {
        ss[s[i]-'a']=true;
    }
    for (int i=0; i<t.size(); i++) {
        tt[t[i]-'a']=true;
    }
    for (int i=0; i<30; i++) {
        if (tt[i]&&!ss[i]) {
            cout<<-1<<endl;
            return 0;
        }
    }
    for (int i=0; i<s.size(); i++) {
        aru[s[i]-'a'].push_back(i+1);
    }
    ans=aru[t[0]-'a'][0];
    now=ans;
    for (int i=1; i<t.size(); i++) {
        int basho=upper_bound(aru[t[i]-'a'].begin(), aru[t[i]-'a'].end(), now)-aru[t[i]-'a'].begin();
        if (basho>=aru[t[i]-'a'].size()) {
            ans+=s.size()-now+aru[t[i]-'a'][0];
            now=aru[t[i]-'a'][0];
        }else{
            ans+=aru[t[i]-'a'][basho]-now;
            now=aru[t[i]-'a'][basho];
        }
//        cout<<aru[t[i]-'a'][basho]<<'n'<<endl;
    }
    cout<<ans<<endl;
}


Measured memory_bytes: 4028