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.Collections.Generic;
using System.Linq;

public class Program
{
  public static void Main()
  {
    var s = Console.ReadLine();
    var t = Console.ReadLine();

    var posList = Enumerable.Range(0, 'z' - 'a' + 1)
      						.Select(x => new List<int>())
      						.ToList();
    
    var text = s + s;
    for (var index = 0; index < text.Length; index++)
    {
      posList[text[index] - 'a'].Add(index);
    }

    long result = 0;

    foreach (var c in t)
    {
      var list = posList[c - 'a'];

      if (!list.Any())
      {
        result = -1;
        break;
      }

      var current = (int)(result % s.Length);
      var next = list.FirstOrDefault(index => index >= current);

      if (next == 0)
      {
        result = -1;
        break;
      }

      result += next - current  + 1;
    }

    Console.WriteLine(result);
  }
}