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;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using static MyIO;
using static BinarySearch;


public class E
{
	public static void Main() => (new Solver()).Solve();
}


public class Solver
{
	public static readonly int INF = int.MaxValue / 2;

	public void Solve()
	{
		string S = GetString();
		string T = GetString();

		long[] cntS = new long[26];
		for(int i = 0; i < S.Length; i++)
			cntS[(int)(S[i] - 'a')]++;

		long[] cntT = new long[26];
		for(int i = 0; i < T.Length; i++)
			cntT[(int)(T[i] - 'a')]++;

		for(int i = 0; i < 26; i++)
		{
			if(cntT[i] != 0 && cntS[i] == 0)
			{
				Console.WriteLine(-1);
				return;
			}
		}

		List<int>[] pos = Enumerable.Range(0, 26).Select(_ => new List<int>()).ToArray();
		for(int i = 0; i < S.Length; i++)
			pos[(int)(S[i] - 'a')].Add(i);

		for(int i = 0; i < 26; i++)
		{
			pos[i].Add(INF);
			pos[i].Sort();
		}

		long ans = 0;
		int current = -1;
		Comparison<int> comp = (x, y) => x - y;
		for(int i = 0; i < T.Length; i++)
		{
			int c = (int)(T[i] - 'a');
			int lb = LowerBound(pos[c], current + 1, comp);
			if(pos[c][lb] == INF)
			{
				ans += S.Length - current - 1;
				current = -1;
				lb = LowerBound(pos[c], current + 1, comp);
			}
			ans += pos[c][lb] - current;
			current = pos[c][lb];
		}

		Console.WriteLine(ans);
	}
}


public static class BinarySearch
{
	public static int LowerBound<T>(List<T> array, T key, Comparison<T> comp)
	{
		int len = array.Count;
		if(comp(array[len - 1], key) < 0)
			return -1;

		int left = 0;
		int right = len - 1;
		while(right > left)
		{
			int mid = (left + right) / 2;
			if(comp(array[mid], key) >= 0)
				right = mid;
			else
				left = mid + 1;
		}

		return left;
	}

	public static int UpperBound<T>(List<T> array, T key, Comparison<T> comp)
	{
		int len = array.Count;
		if(comp(array[len - 1], key) <= 0)
			return len;

		int left = 0;
		int right = len - 1;
		while(right > left)
		{
			int mid = (left + right) / 2;
			if(comp(array[mid], key) > 0)						
				right = mid;
			else			
				left = mid + 1;	
		}

		return left;
	}
}


public static class MyIO
{
	private static string[] args = null;
	private static int num = -1;
	private static int used = -1;

	private static string getArg()
	{
		if(used == num)
		{
			args = Console.ReadLine().Split(' ');
			num = args.Length;
			used = 0;
		}
		return args[used++];
	}

	public static int GetInt() => int.Parse(getArg());
	public static long GetLong() => long.Parse(getArg());
	public static double GetDouble() => double.Parse(getArg());
	public static string GetString() => getArg();
	public static char GetChar() => getArg()[0];
}