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: Time Limit Exceeded)

import java.util.*;
import java.lang.*;

public class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		String t = sc.next();
		int mod = s.length();
		long ans = 0;
		TreeSet<Integer>[] index = new TreeSet[26];
		for (int i = 0; i < 26; i++) {
			index[i] = new TreeSet<>();
		}
		for (int i = 0; i < t.length(); i++) {
			TreeSet<Integer> tmp = index[t.charAt(i) - 'a'];
			if (tmp.size() == 0) {
				if (s.indexOf(t.charAt(i)) == -1) {
					ans = -1;
					break;
				} else {
					int in = 0;
					while (s.indexOf(t.charAt(i), in) != -1) {
						tmp.add(s.indexOf(t.charAt(i), in));
						in = s.indexOf(t.charAt(i), in) + 1;
					}
				}
			}
			int num = -1;
			for (int key: tmp) {
				if (key >= ans % mod) {
					num = key;
					break;
				}
			}
			if (num == -1) {
				num = tmp.first();
			}
			if (num + 1 <= ans % mod) {
				ans = mod * ((ans + mod - 1) / mod) + num + 1;
			} else {
				ans = mod * (ans / mod) + num + 1;
			}
		}
		System.out.println(ans);
	}
}