import java.io.*;
import java.math.BigInteger;
import java.text.DecimalFormat;
import java.util.*;

public class Main {

    static InputReader sc = new InputReader(System.in);
    static PrintWriter out = new PrintWriter(System.out);

    public static void main(String[] args) throws IOException {
        solver s = new solver();
        long t = 1;
        while (t > 0) {
            s.solve();
            t--;
        }
        out.close();
    }

   /* static class descend implements Comparator<pair1> {
        public int compare(pair1 o1, pair1 o2) {
            if (o1.pop != o2.pop)
                return (int) (o1.pop - o2.pop);
            else
                return o1.in - o2.in;
        }
    }*/

    static class InputReader {
        public BufferedReader br;
        public StringTokenizer token;

        public InputReader(InputStream stream) {
            br = new BufferedReader(new InputStreamReader(stream), 32768);
            token = null;
        }

        public String next() {
            while (token == null || !token.hasMoreTokens()) {
                try {
                    token = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return token.nextToken();
        }

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

        public String nextLine() throws IOException {
            return br.readLine();
        }

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

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }

    static class card {
        long a;
        int cnt;
        int i;

        public card(long a, int cnt, int i) {
            this.a = a;
            this.cnt = cnt;
            this.i = i;
        }
    }

    static class ascend implements Comparator<pair> {
        public int compare(pair o1, pair o2) {
            if (o1.a != o2.a)
                return (int) (o1.a - o2.a);
            else
                return o1.b - o2.b;
        }
    }

    static class extra {

        static boolean v[] = new boolean[100001];
        static List<Integer> l = new ArrayList<>();
        static int t;

        static void shuffle(int a[]) {
            for (int i = 0; i < a.length; i++) {
                int t = (int) Math.random() * a.length;
                int x = a[t];
                a[t] = a[i];
                a[i] = x;
            }
        }

        static long gcd(long a, long b) {
            if (b == 0)
                return a;
            else
                return gcd(b, a % b);
        }

        static boolean valid(int i, int j, int r, int c, char ch[][]) {
            if (i >= 0 && i < r && j >= 0 && j < c && ch[i][j] != '*') {
                // System.out.println(i+" /// "+j);
                return true;
            } else {
                //  System.out.println(i+" //f "+j);
                return false;
            }
        }

        static void seive() {
            for (int i = 2; i < 100001; i++) {
                if (!v[i]) {
                    t++;
                    l.add(i);
                    for (int j = 2 * i; j < 100001; j += i)
                        v[j] = true;
                }
            }
        }

        static int binary(LinkedList<Integer> a, long val, int n) {
            int mid = 0, l = 0, r = n - 1, ans = 0;
            while (l <= r) {
                mid = (l + r) >> 1;
                if (a.get(mid) == val) {
                    r = mid - 1;
                    ans = mid;
                } else if (a.get(mid) > val)
                    r = mid - 1;
                else {
                    l = mid + 1;
                    ans = l;
                }
            }
            return (ans + 1);
        }

        static long fastexpo(long x, long y) {
            long res = 1;
            while (y > 0) {
                if ((y & 1) == 1) {
                    res *= x;
                }
                y = y >> 1;
                x = x * x;
            }
            return res;
        }

        static long lfastexpo(long x, long y, long p) {
            long res = 1;
            x = x % p;
            while (y > 0) {
                if ((y & 1) == 1) {
                    res = (res * x) % p;
                }
                y = y >> 1;
                x = (x * x) % p;
            }
            return res;
        }

       /* void dijsktra(int s, List<pair> l[], int n) {
            PriorityQueue<pair> pq = new PriorityQueue<>(new ascend());
            int dist[] = new int[100005];
            boolean v[] = new boolean[100005];
            for (int i = 1; i <= n; i++)
                dist[i] = 1000000000;
            dist[s] = 0;
            for (int i = 1; i < n; i++) {
                if (i == s)
                    pq.add(new pair(s, 0));
                else
                    pq.add(new pair(i, 1000000000));
            }
            while (!pq.isEmpty()) {
                pair node = pq.remove();
                v[node.a] = true;
                for (int i = 0; i < l[node.a].size(); i++) {
                    int v1 = l[node.a].get(i).a;
                    int w = l[node.a].get(i).b;
                    if (v[v1])
                        continue;
                    if ((dist[node.a] + w) < dist[v1]) {
                        dist[v1] = dist[node.a] + w;
                        pq.add(new pair(v1, dist[v1]));
                    }
                }
            }
        }*/
    }

    static class pair {
        int a;
        int b;

        public pair(int a, int i) {
            this.a = a;
            this.b = i;
        }
    }

    static class pair1 {
        pair p;
        int in;

        public pair1(pair a, int n) {
            this.p = a;
            this.in = n;
        }
    }


    static int inf = 5000013;

    static class solver {
        DecimalFormat df = new DecimalFormat("0.000000");
        extra e = new extra();
        int mod = 1000000007;
        int in[][] = new int[2][2];
        List<pair> l = new ArrayList<>();

        void solve() {
            char s[] = sc.next().toCharArray();
            char t[] = sc.next().toCharArray();
            int len1 = s.length;
            int len2 = t.length;
            TreeSet<Long> set[] = new TreeSet[26];
            for (int i = 0; i < 26; i++)
                set[i] = new TreeSet<>();
            int f[] = new int[26];
            int f2[] = new int[26];
            for (int i = 0; i < len1; i++) {
                int t1 = s[i] - 'a';
                f[t1]++;
                set[t1].add((long)i+1);
            }
            for (int i = 0; i < len2; i++) {
                f2[t[i] - 'a']++;
            }
            boolean b = true;
            for (int i = 0; i < 26; i++) {
                if (f2[i] > 0 && f[i] == 0) {
                    b = false;
                    break;
                }
            }
            if (!b)
                System.out.println("-1");
            else {
                long in = -1, pre;
                for (Long h : set[t[0] - 'a']) {
                    in = h;
                    break;
                }
                pre = in;
                for (int i = 1; i < len2; i++) {
                    int ch = t[i] - 'a';
                    Long cur = set[ch].higher(pre);
                    int f1 = 0;
                    if (cur == null) {
                        f1 = 1;
                        cur = set[ch].ceiling(1l);
                    }
                    if (f1 == 1)
                        in += cur + (len1 - pre);
                    else
                        in += cur - pre;
                    pre = cur;
                }
                System.out.println(in);
            }
        }
    }
}




Measured memory_bytes: 37412