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: Wrong Answer)

import java.util.*;
import java.io.*;
public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		char[] s = br.readLine().toCharArray();
		long n = s.length;
		char[] t = br.readLine().toCharArray();
		TreeSet<Integer>[] poss = new TreeSet[26];
		for(int c = 0; c < 26; c++){
			poss[c] = new TreeSet<>();
		}
		for(int i = 0; i < n; i++){
			poss[s[i]-'a'].add(i);
		}
		int prev = 0;
		long count = 0;
		for(char c: t){
			if(poss[c-'a'].isEmpty()){
				System.out.println("-1"); return;
			}
			Integer curr = poss[c-'a'].higher(prev);
			if(curr == null){
				curr = poss[c-'a'].first();
				count++;
				prev = curr;
			}
			else{
				prev = curr;
			}
		}
		System.out.println(((long)count) * n + (long)prev + 1L);
	}

}