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.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String s = br.readLine();
        String t = br.readLine();
        
        List<TreeSet<Integer>> table = new ArrayList<>(26);
        for(int i = 0; i < 26; i++){
            table.add(new TreeSet<>());
        }
        
        for(int i = 0; i < s.length(); i++){
            int k = s.charAt(i) - 'a';
            table.get(k).add(i);
            table.get(k).add(i + s.length());
        }
        
        long base = 0;
        int idx = -1;
        for(int i = 0; i < t.length(); i++){
            int k = t.charAt(i) - 'a';
            Integer j = table.get(k).higher(idx);
            if( j == null ){
                System.out.println(-1);
                return;
            }
            
            idx = j;
            if(idx >= s.length()){
                base += s.length();
                idx -= s.length();
            }
        }
        
        System.out.println(base + idx + 1);
        
    }
}