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;//リストの使用
using System.Collections.Generic;
using System.Text;//テキストの高速出力に必要
class Program
{
static string s = Console.ReadLine();
static long sn = s.Length;
static string t = Console.ReadLine();
static long tn = t.Length;
static List<long>[] alphabetsList = new List<long>[26];//a,b…があるのは何文字めか
static long lookingNum = sn;//何文字目を見ているか
static long answer = 0;

	static void Main()
	{
    for(long i = 0; i < 26; i++)
    {
      alphabetsList[i] = new List<long>();
    }

    for(long i = 0; i < sn; i++)
    {
      alphabetsList[s[(int)i]-'a'].Add(i+1);
    }

    for(long i = 0; i < tn; i++)
    {
      long alphaCount = alphabetsList[t[(int)i]-'a'].Count;
      
      if(alphaCount == 0)
      {
        answer = -1;
        break;
      }

      if(alphabetsList[t[(int)i]-'a'][(int)alphaCount-1] <= lookingNum)//1周
      {
        answer += sn-lookingNum;
        answer += alphabetsList[t[(int)i]-'a'][0];
        lookingNum = alphabetsList[t[(int)i]-'a'][0];
      }else
      {
        long nextNum = alphabetsList[t[(int)i]-'a'][(int)Search(0,alphaCount-1,-1,t[(int)i]-'a')];
        answer += nextNum-lookingNum;
        lookingNum = nextNum;
      }
    }

		Console.WriteLine(answer);
	}

  static long Search(long min, long max, long MinorMax, long listNum)//二分探索法で最小値-1最大値1を求める
  {
    while (true)
    {
      long mid = min + (max - min) / 2;
      if(MinorMax == 1)
      {
        if(Check(mid,listNum)) min = mid;//さらに大きくても成り立つかも
        else max = mid;
      }else
      {
        if(Check(mid,listNum)) max = mid;//さらに小さくても成り立つかも
        else min = mid;
      }

      if(max - min <= 1)
      {
        if(MinorMax == 1)
        {
          if(Check(max,listNum)) return max;//最大値で成り立つかの確認を優先
          else return min;
        }else
        {
          if(Check(min,listNum)) return min;//最小値で成り立つかの確認を優先
          else return max;
        }

      break;
      }  
    }
  }

  static bool Check(long testNum, long listNum)
  {
    if(lookingNum < alphabetsList[(int)listNum][(int)testNum]) return true;
    return false;
  } 
  
}