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: Wrong Answer)

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 = Console.ReadLine();
      var t = Console.ReadLine();
      var tMap = new Dictionary<char, LinkedList<int>>();
      var ss = s + s;
      foreach (var c in t.Distinct())
      {
        var indexList = getIndexList(c, ss);
        if (!indexList.Any())
        {
          return -1;
        }
        tMap[c] = indexList;
      }

      var pos = 0;
      var ans = 0L;
      foreach (var c in t)
      {
        var indexList = tMap[c];
        pos = indexList.FirstOrDefault(i => i > pos);
        if (pos / s.Length > 0)
        {
          // loop
          ans += s.Length;
          pos = indexList.First();
        }
      }
      ans += pos;

      return ans;
    }
    private static LinkedList<int> getIndexList(char c, string ss)
    {
      var ret = new LinkedList<int>();
      var befIndex = -1;
      var index = ss.IndexOf(c, befIndex + 1);
      var slength = ss.Length / 2;
      while (index >= 0 && slength > index)
      {
        ret.AddLast(index + 1);
        befIndex = index;
        index = ss.IndexOf(c, befIndex + 1);
      }
      ret.AddLast(index + 1);
      return ret;
    }
  }
}