Problem:
Score : 500 points

Problem Statement

Given are two strings s and t consisting of lowercase English letters. Determine if there exists an integer i satisfying the following condition, and find the minimum such i if it exists.

Let s' be the concatenation of 10^{100} copies of s. t is a subsequence of the string {s'}_1{s'}_2\ldots{s'}_i (the first i characters in s').

Notes

A subsequence of a string a is a string obtained by deleting zero or more characters from a and concatenating the remaining characters without changing the relative order. For example, the subsequences of contest include net, c, and contest.

Constraints

1 \leq |s| \leq 10^5

1 \leq |t| \leq 10^5

s and t consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s
t

Output

If there exists an integer i satisfying the following condition, print the minimum such i; otherwise, print -1.

Sample Input 1

contest
son

Sample Output 1

10

t = son is a subsequence of the string contestcon (the first 10 characters in s' = contestcontestcontest...), so i = 10 satisfies the condition.

On the other hand, t is not a subsequence of the string contestco (the first 9 characters in s'), so i = 9 does not satisfy the condition.

Similarly, any integer less than 9 does not satisfy the condition, either. Thus, the minimum integer i satisfying the condition is 10.

Sample Input 2

contest
programming

Sample Output 2

-1

t = programming is not a substring of s' = contestcontestcontest.... Thus, there is no integer i satisfying the condition.

Sample Input 3

contest
sentence

Sample Output 3

33

Note that the answer may not fit into a 32-bit integer type, though we cannot put such a case here.

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace AtCoder.E
{
    public class Program
    {
        private static string _s;
        private static string _t;

        public static void Main() { var r = GetResult(); Debug.WriteLine(r); Console.Write(r); }

        private static object GetResult()
        {
            _s = ReadText();
            _t = ReadText();

            if (HasNoAnswer(_s, _t))
            {
                return -1;
            }

            var ss = new Dictionary<char, List<int>>();
            for (var i = 0; i < _s.Length; i++)
            {
                var key = _s[i];
                if (!ss.ContainsKey(key))
                {
                    ss[key] = new List<int>();
                }
                ss[key].Add(i);
            }

            var sInfo = new Dictionary<char, Info>();
            foreach (var item in ss)
            {
                sInfo.Add(item.Key, new Info(item, _s.Length));
            }

            var answer = 0L;
            var s_preIndex = -1;
            var s_currentIndex = 0;
            for (int i = 0; i < _t.Length; i++)
            {
                var currentChar = _t[i];
                var info = sInfo[currentChar];
                if (!info.HasChar(s_currentIndex))
                {
                    s_currentIndex = info.NextCharIndex(s_currentIndex);
                }

                if (s_preIndex < s_currentIndex)
                {
                    answer += s_currentIndex - s_preIndex;
                }
                else
                {
                    // 一周していた場合
                    answer += _s.Length - s_preIndex + s_currentIndex;
                }

                s_preIndex = s_currentIndex;

                s_currentIndex++;
                // 端まで到達していた場合
                if (s_currentIndex == _s.Length)
                {
                    s_currentIndex = 0;
                }
            }

            return answer;
        }

        private static bool HasNoAnswer(string s, string t)
        {
            var sHash = new HashSet<char>();
            var tHash = new HashSet<char>();
            for (var i = 0; i < s.Length; i++)
            {
                sHash.Add(s[i]);
            }
            for (var i = 0; i < t.Length; i++)
            {
                tHash.Add(t[i]);
            }

            foreach (var item in tHash)
            {
                if (!sHash.Contains(item)) return true;
            }

            return false;
        }

        #region Console

        public static string ReadText() { return Console.ReadLine(); }
        public static List<string> ReadTexts() { return Console.ReadLine().Split(' ').ToList(); }
        public static long ReadLong() { return long.Parse(Console.ReadLine()); }
        public static List<long> ReadLongs() { return Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToList(); }

        #endregion
    }

    internal class Info
    {
        private readonly bool[] _hasChar;
        private readonly int[] _nextIndexes;

        public Info(KeyValuePair<char, List<int>> item, int sLength)
        {
            _hasChar = new bool[sLength];
            _nextIndexes = new int[sLength];
            foreach (var v in item.Value)
            {
                _hasChar[v] = true;
            }

            var nextIndexIndex = 0;
            var itemValueCount = item.Value.Count;
            var nextIndex = item.Value[nextIndexIndex];
            for (int i = 0; i < sLength; i++)
            {
                if (!_hasChar[i])
                {
                    _nextIndexes[i] = nextIndex;
                }
                else
                {
                    nextIndexIndex++;
                    if (nextIndexIndex == itemValueCount)
                    {
                        nextIndexIndex = 0;
                    }
                    nextIndex = item.Value[nextIndexIndex];
                    _nextIndexes[i] = nextIndex;
                }
            }
        }

        public bool HasChar(int index)
        {
            return _hasChar[index];
        }
        public int NextCharIndex(int index)
        {
            return _nextIndexes[index];
        }
    }
}