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;

namespace ABC138
{
    class E
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            string t = Console.ReadLine();

            Dictionary<char, List<long>> dict = new Dictionary<char, List<long>>();

            for (int i = 0; i < s.Length; i++)
            {
                if (!dict.ContainsKey(s[i]))
                {
                    dict.Add(s[i], new List<long>());
                    dict[s[i]].Add(i);
                }
                else if (dict.ContainsKey(s[i]))
                {
                    dict[s[i]].Add(i);
                }
            }

            // NGの時
            for (int i = 0; i < t.Length; i++)
            {
                if (!dict.ContainsKey(t[i])) { Console.WriteLine(-1); return; }
            }

            //<--debug
            //for (int i = 0; i < t.Length; i++)
            //{
            //    Console.WriteLine(string.Join(" ", dict[t[i]]));
            //}
            //debug-->

            long count = 1;
            long current = 0;
            int index = 0;

            foreach (var c in t)
            {
                var list = dict[c];

                index = list.BinarySearch(current);
                if (index < 0) { index = ~index; }
                if (list.Count <= index) { index = 0; }

                if (list[index] < current)
                {
                    count += (long)s.Length - (current + 1) + list[index] + 1;
                    current = list[index];
                }
                else
                {

                    count += list[index] - current;
                    current = list[index];
                }
                //Console.WriteLine("count : " + count);
            }

            Console.WriteLine(count);
        }
    }
}