#include <bits/stdc++.h>
#define ll long long
using namespace std;
typedef long double ld;
char s[100050],t[100050];
int n,m;
ll ans;
vector <int> v[30+'a'];

int main(){
	scanf("%s",s);
	scanf("%s",t);
	n=strlen(s),m=strlen(t);
	for(int i=0;i<n;++i){
		v[s[i]].push_back(i);
	}
	int p1=-1;
	for(int i=0;i<m;++i){
		char c=t[i];
		if(v[c].empty())return puts("-1"),0;
		auto it=upper_bound(v[c].begin(),v[c].end(),p1);
		if(it==v[c].end()){
			it=v[c].begin();
			ans++;
		}
		p1=*it;
	}
	cout<<ans*1LL*strlen(s)+p1+1<<endl;
	return 0;
}