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;
using System.Linq;


namespace AtCoder
{
    partial class Program
    {
        static void Main(string[] args)
        {
			//↓

            var s = Console.ReadLine();
            var t = Console.ReadLine();

            var sset = new HashSet<char>(s);
            var tset = new HashSet<char>(t);

            if (!tset.All(tc => sset.Contains(tc)))
            {
                Console.WriteLine(-1);
                return;
            }


            var cd = new Dictionary<char, List<int>>();
            for (int i = 0; i < s.Length; i++)
            {
                var c = s[i];
                List<int> l;
                if (cd.TryGetValue(c, out l))
                {
                    l.Add(i);
                }
                else
                {
                    l = new List<int>();
                    l.Add(i);
                    cd[c] = l;
                }
            }

            var d = new Dictionary<char, int[]>();
            foreach (var kv in cd)
            {
                d[kv.Key] = kv.Value.ToArray();
            }


            long count = 0;
            int j = -1;
            for (int i = 0; i < t.Length; i++)
            {
                var c = t[i];
                var l = d[c];
                
                var ji = Array.BinarySearch(l, j);
                if (ji < 0)
                {
                    ji = ~ji;

                    if (ji < l.Length)
                    {
                        j = l[ji];
                    }
                    else
                    {
                        count += s.Length;
                        j = l[0];
                        continue;
                    }
                }
                else
                {
                    if (ji + 1 >= l.Length)
                    {
                        count += s.Length;
                        j = l[0];
                        continue;
                    }

                    j = l[ji + 1];
                }
                
                if (j > -1)
                {
                    continue;
                }
                else
                {
                    

                    count += s.Length;
                    j = l[0];
                }
            }
            count += j + 1;

            Console.WriteLine(count);


			//↑
        }
	}
}