using System;
using System.Collections.Generic;
using System.Linq;
using BitArray = System.Collections.BitArray;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;
using System.Text;

namespace AtCoderProject
{
    public class Program
    {
        public object Calc()
        {
            s = consoleReader.String.Select(c => c - 'a').ToArray();
            var t = consoleReader.String.Select(c => c - 'a').ToArray();
            if (t.Except(s).Any()) return -1;
            var tmp = new List<int>[]{
                new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
            new List<int>(),
        };
            for (int i = 0; i < s.Length; i++)
                tmp[s[i]].Add(i);
            origIndexes = tmp.Select(list => Init(list)).ToArray();
            current = origIndexes[t[0]][0];
            for (int i = 1; i < t.Length; i++)
            {
                UpdateCurrent(origIndexes[t[i]]);
            }
            return count * s.Length + current + 1;
        }
        int[] Init(List<int> list)
        {
            var res = Enumerable.Repeat(-1, s.Length + 1).ToArray();
            if (list.Count == 0) return res;
            var listIndex = 0;
            for (int i = 0; i < res.Length; i++)
            {
                if (i < list[listIndex])
                    res[i] = list[listIndex];
                else if (i == list[listIndex])
                {
                    res[i] = list[listIndex++];
                    if (listIndex >= list.Count) break;
                }
            }
            return res;
        }
        void UpdateCurrent(int[] orig)
        {
            var next = orig[current + 1];
            if (next >= 0) {
                current = next;
            }
            else
            {
                count++;
                current = orig[0];
            }
        }
        int current;
        long count = 0;
        int[] s;
        int[][] origIndexes;

        #region いつもの
        private readonly ConsoleReader consoleReader;
        public Program(ConsoleReader consoleReader) { this.consoleReader = consoleReader; }
        static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.In)).Calc()); static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
        #endregion
    }
    class GraphBuilder
    {
        private List<int>[] lists;
        public GraphBuilder(int count)
        {
            this.lists = new List<int>[count];
            for (int i = 0; i < count; i++)
                this.lists[i] = new List<int>();
        }
        public GraphBuilder(int count, IEnumerable<int[]> arrays) : this(count)
        {
            foreach (var item in arrays)
                this.Add(item[0], item[1]);
        }
        public void Add(int from, int to)
        {
            this.lists[from].Add(to);
        }
        public int[][] ToArray()
        {
            var N = this.lists.Length;
            var res = new int[N][];
            for (int i = 0; i < N; i++)
                res[i] = this.lists[i].ToArray();
            return res;
        }
    }

#pragma warning disable
    public class ConsoleReader
    {
        private string[] line = Array.Empty<string>();
        private int linePosition;
        private TextReader textReader;
        public ConsoleReader(TextReader tr) { textReader = tr; }
        public int Int => int.Parse(String);
        public long Long => long.Parse(String);
        public double Double => double.Parse(String);
        public string String
        {
            get
            {
                if (linePosition >= line.Length)
                {
                    linePosition = 0;
                    line = textReader.ReadLine().Split();
                }
                return line[linePosition++];
            }
        }
        public class SplitLine
        {
            private string[] splited;
            public SplitLine(ConsoleReader cr) { splited = cr.textReader.ReadLine().Split(); }
            public int[] Int => String.Select(x => int.Parse(x)).ToArray();
            public long[] Long => String.Select(x => long.Parse(x)).ToArray();
            public double[] Double => String.Select(x => double.Parse(x)).ToArray();
            public string[] String => splited;
        }
        public SplitLine Split => new SplitLine(this);
        public class RepeatReader
        {
            ConsoleReader cr; int count;
            public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; }
            public IEnumerable<T> Select<T>(Func<ConsoleReader, T> func) { for (int i = 0; i < count; i++) yield return func(cr); }
            public IEnumerable<string> String { get { for (int i = 0; i < count; i++) yield return cr.String; } }
            public IEnumerable<int> Int { get { for (int i = 0; i < count; i++) yield return cr.Int; } }
            public IEnumerable<double> Double { get { for (int i = 0; i < count; i++) yield return cr.Double; } }
        }
        public RepeatReader Repeat(int count) => new RepeatReader(this, count);
    }
}

Measured memory_bytes: 36580