import java.util.*; import java.io.*; import java.math.*;
public class Main{
	//Don't have to see. start------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<String>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			try{
				while((read = br.readLine()) != null){
					inputLine.add(read);
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<Integer, String>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object t){System.err.print("debug:");System.err.println(t);}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextStrArray(){return myconv(next(), 8);}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<Integer> nextIntArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Integer> ret = new ArrayList<Integer>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Integer.parseInt(input.get(i)));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Long> ret = new ArrayList<Long>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Long.parseLong(input.get(i)));
		}
		return ret;
	}
	static String myconv(Object list, int no){//only join
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof ArrayList){
			return String.join(joinString, (ArrayList)list);
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//Don't have to see. end------------------------------------------
	static void solve(){//Here is the main function
			ArrayList<String> s = nextCharArray();
			ArrayList<String> t = nextCharArray();
			HashMap<String, ArrayList<Integer>> map = new HashMap<String, ArrayList<Integer>>();
			long output = 0;
			for(int i = 0; i < s.size(); i++){
				ArrayList<Integer> tmp;
				if(map.containsKey(s.get(i))){
					tmp = map.get(s.get(i));
				}else{
					tmp = new ArrayList<Integer>();
				}
				tmp.add(i);
				map.put(s.get(i), tmp);
			}
			int maeIndex = -1;
			long loop = 0;
			for(int i = 0; i < t.size(); i++){
				if(!map.containsKey(t.get(i))){
					myout(-1);
					return;
				}
				ArrayList<Integer> tmp = map.get(t.get(i));
				if(i == 0){
					output = tmp.get(0) + 1;
					maeIndex = tmp.get(0);
				}else{
					int index = binarySearch(tmp, maeIndex);
					if(index == tmp.size() || tmp.get(index) == maeIndex){
						loop++;
						index = 0;
					}
					output = (loop * s.size()) + tmp.get(index) + 1;
					maeIndex = tmp.get(index);
				}
			}
			myout(output);
	}
	//Method addition frame start

static int binarySearch(ArrayList<Integer> list,int search){
  int ng = -1;
  int ok = list.size();
  while(Math.abs(ok - ng) > 1){
    int center = (ok + ng) / 2;
    if(list.get(center) > search){
      ok = center;
    }else{
      ng = center;
    }
  }
  return ok;
  //return list.get(ng);
}


	//Method addition frame end
}


Measured memory_bytes: 64616