#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#define each(it,o) for(auto it= (o).begin(); it != (o).end(); ++ it)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define inrep int t;cin>>t; while(t--)
using namespace std;
using namespace __gnu_pbds; 


typedef long long int ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef vector<pii > vpii;
typedef vector<ll> vll;
typedef pair<ll,ll> pll;
typedef vector<pll > vpll; 
typedef vector<string> vs;
typedef long double ld;
const ll MOD = 1e9+7;
template<typename T> istream& operator>> ( istream &in,vector<T> &v ) {

    for ( unsigned   i=0; i<v.size(); i++ )
        in>>v[i];
    return in;
}
int main()
{
    // #ifndef ONLINE_JUDGE
    // freopen("input.txt","r",stdin);
    // freopen("output.txt","w",stdout);
    // #endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    string s,t;
    cin>>s>>t;
    ll ls=s.length();
    ll lt=t.length();
    ll as[26]={0};
    ll at[26]={0};
    vector<ll> a[26];
    for(ll i=0;i<ls;i++)
    {
        as[s[i]-97]++;
        a[s[i]-97].push_back(i);
    }
    for(ll i=0;i<lt;i++)
    {
        at[t[i]-97]++;
    }
    ll flag=0;
    ll siz[26]={0};
    for(ll i=0;i<26;i++)
    {
        if(at[i]!=0)
        {
            if(as[i]==0)
            {
                flag=1;
                break;
            }
        }
    }
    if(flag==1)
    {
        cout<<"-1";
    }
    else
    {
        ll k=0;ll sz=0;ll tmp=0;
        while(k!=lt)
        {
            if(siz[t[k-97]]==a[t[k]-97].size())
            {
                for(ll i=0;i<26;i++)
                {
                    siz[i]=0;
                }
                tmp=0;
                sz++;
            }
            else
            {
                if(a[t[k]-97][siz[t[k]-97]]<=tmp)
                {
                    sz++;
                    tmp=a[t[k]-97][0];
                    for(ll i=0;i<26;i++)
                 {
                    siz[i]=0;
                }
                    siz[t[k]-97]++;
                }
                else
                {
                    tmp=a[t[k]-97][siz[t[k]-97]];
                    siz[t[k]-97]++;
                }
            }
            k++;
        }
        ll d = sz*ls+tmp;
        cout<<d+1;
    }
    // #ifndef ONLINE_JUDGE
    //     cout<<"\nTime Elapsed : "<< 1.0*clock() / CLOCKS_PER_SEC << " s\n";
    // #endif
    
    return 0;
}