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 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 + 1);
      }

      var pos = 0;
      var ans = 0L;
      foreach (var c in t)
      {
        var indexList = map[c];
        pos = indexList.HigherOrDefault(pos);
        if (pos == 0)
        {
          ans += s.Length;
          pos = indexList.First();
        }
      }
      ans += pos;

      return ans;
    }
  }

  public static class ListExtensions
  {
    public static int HigherOrDefault(this List<int> sorted, int t)
    {
      return SearchHigher(sorted, t);
    }

    private static int SearchHigher(List<int> sorted, int t)
    {
      var count = sorted.Count();
      if (count < 2)
      {
        return t < sorted.First() ? sorted.First() : default(int);
      }
      var val = sorted[count / 2];
      if (t < val)
      {
        return SearchHigher(sorted.Take(count / 2).ToList(), t);
      }
      else
      {
        return SearchHigher(sorted.Skip(count / 2).ToList(), t);
      }
    }
  }
}