#include<bits/stdc++.h>
#define IO ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define pb                          push_back
#define all(x)                      (x).begin(),(x).end()
#define ll                          long long
#define ld                          long double
#define eps                         1e-9
#define sz(a)                       (ll)(a).size()
#define ppc                         __builtin_popcount
#define ppcll                       __builtin_popcountll
#define endl                        "\n"
#define lb                          lower_bound
#define ub                          upper_bound
const ld PI = acos(-1.0);
const int MOD = 1e9 +7;
const ll INF = 1e18;
// if(abs(a-b)<eps) --> if(a==b)
// fixed << setprecision(n) -->printing decimal till n
// hypot(a ,b) --> sqrt(a^2 + b^2)
using namespace std;

void solve(){
    string s,t1;
    cin>>s>>t1;
    vector<vector<ll>>dp(26);
    for(int i=0;i<sz(s);i++){
        dp[s[i]-'a'].pb(i);
    }

    ll ind =0;
    ll copies =1;
    for(int i=0;i<sz(t1);i++){
        if(dp[t1[i]-'a'].size()==0){
            cout<<-1<<endl;
            return;
        }

        auto it = lb(all(dp[t1[i]-'a']) , ind);
        if(it==dp[t1[i]-'a'].end()){
            //again chekcing
            ind =0;
            copies++;
            auto it1 = lb(all(dp[t1[i]-'a']) , ind);
            ind = *it1;
        }
        else{
            ind = *it;
        }
    }

    cout<<copies*sz(s) - sz(s) + ind+1 <<endl;
}

int main(){
    IO;
    ll t =1;
    // cin>>t;
    for(int i=1;i<=t;i++){
        // cout<<"Case #"<<i<<": ";
        solve();
    }
    return 0;
}