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;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;

static class CodeJam
{
    static long Solve(string S, string T)
    {
        var lists = new List<int>[26];
        for (int i = 0; i < 26; ++i)
        {
            lists[i] = new List<int>();
        }
        for (int i = 0; i < S.Length; ++i)
        {
            lists[S[i] - 'a'].Add(i);
        }
        int a = 0, b = -1;
        foreach (char t in T)
        {
            int i = t - 'a';
            int N = lists[i].Count;
            if (N == 0) { return -1; }
            Func<int> search = () =>
            {
                int L = 0, R = N - 1;
                if (b < lists[i][0]) { return 0; }
                if (lists[i][R] <= b) { return N; }
                while (R - L >= 2)
                {
                    int m = (L + R) / 2;
                    if (b < lists[i][m]) { R = m; } else { L = m; }
                }
                return R;
            };
            int j = search();
            if (j < N)
            {
                b = lists[i][j];
            }
            else
            {
                b = lists[i][0];
                ++a;
            }
        }
        return Math.BigMul(S.Length, a) + b + 1;
    }

    static void Main(string[] args)
    {
        string S = Console.ReadLine();
        string T = Console.ReadLine();
        Console.WriteLine(Solve(S, T));
    }
}