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.*;

public class Main{
    
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        
        char[] s = sc.next().toCharArray();
        char[] t = sc.next().toCharArray();
        
        TreeSet<Integer>[] al = new TreeSet[26];
        for(int i=0; i<26; i++){
            al[i] = new TreeSet<>();
        }
        
        int len = s.length;
        for(int i=0; i<len; i++){
            int idx = s[i]-97;
            al[idx].add(i);
        }
        
        long ans = 0L;
        int cur = -1;
        for(int i=0; i<t.length; i++){
            int idx = t[i]-97;
            Integer next = al[idx].higher(cur);
            if(next==null && al[idx].size()==0){
                System.out.println(-1);
                return;
            }else if(next==null){
                ans += len-cur-1;
                next = al[idx].higher(-1);
                ans += next+1;
                cur = next;
            }else{
                ans += next-cur;
                cur = next;
            }
        }
        
        System.out.println(ans);
        
    }
}