#include <algorithm>
#include <complex>
#include <cstdlib>
#include <ctime>
#include <time.h>
#include <iomanip>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

using namespace std;
#define SAY_YES cout << "YES" << endl;
#define SAY_Yes cout << "Yes" << endl;
#define SAY_NO cout << "NO" << endl;
#define SAY_No cout << "No" << endl;
#define IFYES(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "YES" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "NO" << endl;  \
    }
#define IFYes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "Yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "No" << endl;  \
    }
#define IFyes(TRUE_OR_FALSE)   \
    if (TRUE_OR_FALSE)         \
    {                          \
        cout << "yes" << endl; \
    }                          \
    else                       \
    {                          \
        cout << "no" << endl;  \
    }
#define DEBUG_OUTPUT_ARRAY(XXX, ONE)                            \
    for (int i = 0; i < (ONE); i++)                             \
    {                                                           \
        cout << "DEBUG: i = " << i << " -> " << XXX[i] << endl; \
    }
#define DEBUG_OUTPUT_ARRAY2(XXX, ONE, TWO)                             \
    for (int i = 0; i < (ONE); i++)                                    \
    {                                                                  \
        cout << "<<< i = " << i << " >>>" << endl;                     \
        for (int j = 0; j < (TWO); j++)                                \
        {                                                              \
            cout << "DEBUG: j = " << j << " -> " << XXX[i][j] << endl; \
        }                                                              \
    }
#define DEBUG_OUTPUT_ARRAY2_BOX(XXX, ONE, TWO) \
    for (int i = 0; i < (ONE); i++)            \
    {                                          \
        cout << i << "  ";                     \
        for (int j = 0; j < (TWO); j++)        \
        {                                      \
            cout << XXX[i][j] << " ";          \
        }                                      \
        cout << endl;                          \
    }

typedef pair<long long int, long long int> pll;


const long long int mod = 1000000007;
const long long int INF = 99999999999999999;


long long int N,nearalphabet[30],nextalphabet[200050][30];
string s,s2,t;
vector<long long int>vec;


int main()
{
    cout << fixed << setprecision(18);
    cin>>s>>t;
    s2=s+s;
    for(long long int i = 0; i < 26; i++){
        nearalphabet[i]=INF;
    }
    for(long long int i = s2.size()-1; i >= s.size(); i--){
        nearalphabet[s2[i]-'a']=i-s.size();
    }
    for(long long int i = s.size()-1; i >= 0; i--){
        for(long long int j = 0; j < 26; j++){
            
            nextalphabet[i][j]=nearalphabet[j];
        }
        nearalphabet[s2[i]-'a']=i;
    }
    long long int now=0,fin=0;
    for(long long int i = 0; i < s.size(); i++){
        if(s[i]==t[0]){
            now=i;
            fin=now;
            break;
        }
    }
    //cout<<fin<<endl;
    for(long long int i = 0; i < t.size(); i++){
        if(nearalphabet[t[i]-'a']==INF){
            cout<<-1<<endl;
            return 0;
        }
    }
    for(long long int i = 1; i < t.size(); i++){
        if(nextalphabet[now][t[i]-'a']==INF){
            cout<<-1<<endl;
            return 0;
        }else if(nextalphabet[now][t[i]-'a']>now){
            fin=fin-now+nextalphabet[now][t[i]-'a'];
        }else{
            fin=fin-now+s.size()+nextalphabet[now][t[i]-'a'];
        }
        now=nextalphabet[now][t[i]-'a'];
        //cout<<now<<" "<<fin<<endl;
    }
    cout<<fin+1<<endl;
}


Measured memory_bytes: 25344