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;

public class Solution
{
    public static void Main()
    {
        var s = Console.ReadLine();
        var t = Console.ReadLine();
        var n = s.Length;

        var first = Enumerable.Repeat(-1, 'z' - 'a' + 1).ToArray();
        var next = Enumerable.Range(0, 'z' - 'a' + 1).Select(_ => Enumerable.Repeat(-1, s.Length).ToArray()).ToArray();
        for (int i = 0; i < s.Length; i++)
        {
            var a = s[i] - 'a';
            if (first[a] == -1)
            {
                first[a] = i;
            }
            for (int j = i; j >= 0 && next[a][j] == -1; j--)
            {
                next[a][j] = i;
            }
        }
        for (int a = 0; a < next.Length; a++)
        {
            for (int j = next[a].Length - 1; j >= 0 && next[a][j] == -1; j--)
            {
                next[a][j] = first[a];
            }
        }

        int len = 0;
        var index = 0;
        foreach (var c in t)
        {
            var a = c - 'a';
            var nextIndex = next[a][index];
            if (nextIndex == -1)
            {
                Console.WriteLine(-1);
                return;
            }
            if (nextIndex < index)
            {
                len += n - (index - nextIndex);
            }
            else
            {
                len += nextIndex - index;
            }

            len++;
            index = (nextIndex + 1) % n;
        }

        Console.WriteLine(len);
    }
}