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 static System.Console;

class Program
{
    public static void Main()
    {
	string s = ReadLine();
	string t = ReadLine();

	int N = 'z'-'a'+1;
	
	List<int>[] d0 = new List<int>[N];
	for (int i = 0; i < N; i++)
	{
	    d0[i] = new List<int>();
	}

	for (int i = 0; i < s.Length; i++)
	{
	    char c = s[i];
	    d0[c-'a'].Add(i);
	}

	int [][] d = new int[N][];
	for (int i = 0; i < N; i++)
	{
	    d[i] = d0[i].ToArray();
	}

	int [,] m = new int[s.Length, N];

	for(int i = 0; i < s.Length; i++)
	{
	    for (int j = 0; j < N; j++)
	    {
		if (d[j].Length > 0)
		{
		    int x = Array.BinarySearch(d[j], i);
		    if (x < 0)
		    {
			x = ~x;
			if (x >= d[j].Length){ x = 0; }
		    }
		    int pos = d[j][x];
		    if (pos >= i){ pos -= i; }
		    else         { pos += s.Length - i; }
		    m[i, j] = pos + 1;
		}
	    }
	}

	long ans = 0;
	int ct = 0;
	for(int i = 0; i < t.Length; i++)
	{
	    char c = t[i];
	    int k = m[ct, c-'a'];
	    if (k == 0){ WriteLine(-1); return; }
	    ans += k;
	    ct = (ct + k) % s.Length;
	}

	WriteLine(ans);
    }
}