import java.io.*;
import java.util.Arrays;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.Function;

public class Main {

    static String S, T;

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        S = sc.next();
        T = sc.next();

        System.out.println(solve());
    }

    static long solve() {
        int[] cnt = new int[26];
        int[][] tbl = new int[26][];
        for (int i = 0; i < S.length(); i++) {
            cnt[S.charAt(i)-'a']++;
        }
        for (int i = 0; i < 26; i++) {
            tbl[i] = new int[cnt[i]];
        }
        int[] indice = new int[26];
        for (int i = 0; i < S.length(); i++) {
            int c = S.charAt(i)-'a';
            tbl[c][indice[c]++] = i;
        }

//        for (int i = 0; i < 26; i++) {
//            debug(i, tbl[i]);
//        }

        int round = 0;
        int idx = -1;
        for (int i = 0; i < T.length(); i++) {
            int c = T.charAt(i)-'a';
            // debug(i, T.charAt(i));
            if( cnt[c] == 0 ) return -1;

            int[] cTbl = tbl[c];
            // idxまで読んだ
            int next = lowerBound(cTbl, idx+1);
            // debug(idx, c, cTbl, "next", next, "cnt", cnt[c]);
            if( next >= cnt[c] ) {
                idx = cTbl[0];
                round++;
            } else {
                idx = cTbl[next];
            }
        }
        return (long)round * S.length() + idx + 1;
    }

    static int lowerBound(int[] array, int value) {
        int low = 0;
        int high = array.length;
        int mid;
        while( low < high ) {
            mid = ((high - low) >>> 1) + low; // (high + low) / 2
            if( array[mid] < value ) {
                low = mid + 1;
            } else {
                high = mid;
            }
        }
        return low;
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
    }

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}


Measured memory_bytes: 27220