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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.InputStream;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String s = sc.next();
		String t = sc.next();

		sc.close();

		String s2 = s + s;
		Map<Character, List<Integer>> m = new HashMap<>();
		for (char c = 'a'; c <= 'z'; c++) {
			m.put(c, new ArrayList<>());
		}
		for (int i = 0; i < s2.length(); i++) {
			char c = s2.charAt(i);
			m.get(c).add(i + 1);
		}

		long pos = 0;

		for (int i = 0; i < t.length(); i++) {
			char c = t.charAt(i);
			List<Integer> l = m.get(c);
			if (l.size() == 0) {
				out.println(-1);
				return;
			}
			int idx = upperBound(l, 0, l.size(), (int) (pos % s.length()));

			pos += (l.get(idx) - (int) (pos % s.length()));

		}

		out.println(pos);

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}

	@SuppressWarnings("unused")
	private static int upperBound(List<Integer> a, int st, int ed, int k) {
		if (st == ed - 1) {
			if (a.get(st) <= k) {
				return st + 1;
			} else {
				return st;
			}
		}

		int m = (ed - st) / 2 + st;
		if (a.get(m) <= k) {
			//右側
			return upperBound(a, m, ed, k);
		} else {
			//左側
			return upperBound(a, st, m, k);
		}
	}
}