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# (Mono 4.6.2.0) (judge verdict: Accepted)

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

namespace E
{
  class Program
  {
    static void Main(string[] args)
    {
      Console.WriteLine(Run(args));
    }

    private static long Run(string[] args)
    {
      var s = ConsoleReader.String();
      var t = ConsoleReader.String();

      var td = t.Distinct();
      var sd = s.Distinct();
      if (!td.All(c => sd.Contains(c)))
      {
        return -1;
      }

      var map = sd.ToDictionary(c => c, c => new List<int>());
      for (int i = 0; i < s.Length; i++)
      {
        map[s[i]].Add(i);
      }

      var pos = -1;
      var ans = 0L;
      foreach (var c in t)
      {
        var indexList = map[c];
        var listIndex = indexList.BinarysSearch(i => i > pos);
        if (listIndex > -1)
        {
          // Console.WriteLine(c + " list:" + String.Join(",", indexList));
          // Console.WriteLine("BPos:" + pos);
          pos = indexList[listIndex];
          // Console.WriteLine("APos:" + pos);
        }
        else
        {
          ans += s.Length;
          pos = indexList.First();
        }
      }
      ans += pos + 1;

      return ans;
    }
  }

  public static class ListExtensions
  {
    /// <summary>
    /// 二分探索を行うListの拡張メソッド
    /// <param name="list">拡張対象</param>
    /// <param name="compFunction">比較関数</param>
    /// <return>探索結果のインデックス。マッチしない場合は-1を返す</return>
    /// </summary>
    public static int BinarysSearch<T>(this List<T> list, Func<T, bool> compFunction)
    {
      int left = -1;
      int right = list.Count;

      while (right - left > 1)
      {
        int mid = left + (right - left) / 2;
        if (compFunction(list[mid]))
        {
          right = mid;
        }
        else
        {
          left = mid;
        }
      }
      if (right >= list.Count)
      {
        return -1;
      }
      else
      {
        return right;
      }
    }
  }

  internal static class ConsoleReader
  {
    public static string String()
    {
      return Console.ReadLine();
    }

    public static int Int()
    {
      return int.Parse(Console.ReadLine());
    }

    public static int[] IntArray()
    {
      return Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
    }

    public static long Long()
    {
      return long.Parse(Console.ReadLine());
    }

    public static long[] LongArray()
    {
      return Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
    }

    public static double[] DoubleArray()
    {
      return Console.ReadLine().Split(' ').Select(double.Parse).ToArray();
    }
  }
}