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.Collections.Generic;
class Program
    {
        static void Main(string[] args)
    	{
            string s = Console.ReadLine();
            string t = Console.ReadLine();
            int[,] letter_pos = new int[s.Length, 26];

            int s_size = s.Length;
            for (int i=0; i<s_size; i++)
            {
                int letter = s[i] - 'a';
                for (int j=i; j>=0; j--)
                {
                    if (letter_pos[j, letter] > 0) break;
                    letter_pos[j, letter] = i + 1;
                }
            }
            for (int i=0; i<26; i++)
            {
                if (letter_pos[0, i] == 0) continue;
                for (int j=s_size-1; letter_pos[j, i]==0; j--)
                {
                    letter_pos[j, i] = letter_pos[0, i];
                }
            }

            int pos = 0;
            long ans = 0;
            int t_size = t.Length;
            for (int i=0; i<t_size; i++)
            {
                int letter = t[i] - 'a';
                int buf = letter_pos[pos, letter];
                
                if (pos < buf)
                {
                    ans += buf - pos;
                    pos = buf;
                }
                else{
                    ans += s_size + buf - pos;
                    pos = buf;
                }
                //Console.Error.WriteLine(buf + " " + ans);
                if (pos == 0)
                {
                    Console.WriteLine(-1);
                    return;
                }
                else if(pos == s_size) pos = 0;
            }
            Console.WriteLine(ans);
        }
    }