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.util.Scanner;
import java.util.TreeSet;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String s = scan.nextLine();
		String t = scan.nextLine();

		char[] sChars = s.toCharArray();
		char[] tChars = t.toCharArray();
		long N = s.length();

		// アルファベット分TreeSetを用意
		TreeSet<Integer>[] sets = new TreeSet[26];
		for (int i = 0; i < sets.length; i++) {
			sets[i] = new TreeSet<Integer>();
		}

		// アルファベットに要素順を設定
		for (int i=0; i < sChars.length; i++) {
			sets[sChars[i] - 'a'].add(i);
		}

		int lastIndex = 0;
		long ans = 0;
		for (char c : tChars) {
			Integer tmpIndex = sets[c - 'a'].ceiling(lastIndex);
			if (tmpIndex == null) {
				lastIndex = 0;
				ans += N;
				tmpIndex = sets[c - 'a'].ceiling(lastIndex);
				if (tmpIndex == null) {
					System.out.println(-1);
					return;
				}
			}
			lastIndex = tmpIndex + 1;
		}
		ans = ans + (long)(lastIndex);
		System.out.println(ans);
	}
}