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.IO;
using System.Linq;
using System.Numerics;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Debug = System.Diagnostics.Debug;
using static System.Math;
using System.Runtime.CompilerServices;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;

static class P
{
    static void Main()
    {
        string s = Console.ReadLine();
        string t = Console.ReadLine();
        int[][] nextInds = Enumerable.Repeat(0, s.Length).Select(_ => Enumerable.Repeat(-1, 26).ToArray()).ToArray();
        for (int i = 0; i < 26; i++)
        {
            var targetChar = (char)('a' + i);
            int lastInd = -1;
            for (int j = s.Length - 1; j >= 0; j--)
            {
                nextInds[j][i] = lastInd;
                if (s[j] == targetChar) lastInd = j;
            }
            for (int j = s.Length - 1; j >= 0; j--)
            {
                if (nextInds[j][i] != -1) break;
                nextInds[j][i] = lastInd;
            }
        }
        long sCount = 0;
        int currentInd = s.IndexOf(t[0]);
        if (currentInd == -1)
        {
            Console.WriteLine(-1);
            return;
        }
        foreach (var c in t.Skip(1))
        {
            var nextInd = nextInds[currentInd][c - 'a'];
            if (nextInd == -1)
            {
                Console.WriteLine(-1);
                return;
            }
            if (currentInd >= nextInd) sCount++;
            currentInd = nextInd;
        }
        Console.WriteLine(sCount * s.Length + currentInd + 1);
    }
}