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.util.stream.*;
import java.io.*;

public class Main {

  public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    //String[] in1 = br.readLine().split(" ");
    //int N = Integer.parseInt(in1[0]);
    
    String s = br.readLine();
    String t = br.readLine();
    br.close();

    List<Integer>[] posOfAlph = new List[26];
    for(int i = 0; i < 26; i++) posOfAlph[i] = new ArrayList<Integer>();
    int[] cnt = new int[26];
    for(int i = 0; i < 26; i++) cnt[i] = 0;

    int s_size = s.length();
    int t_size = t.length();

    for(int i = 0; i < s_size; i++){
      posOfAlph[s.charAt(i) - 'a'].add(i);
    }

    long per = 0, prv = -1;

    for(int i = 0; i < t_size; i++){
      int t_char_code = t.charAt(i) - 'a';

      if(posOfAlph[t_char_code].isEmpty()){
        per = -1;
        break;
      }

      if(cnt[t_char_code] == posOfAlph[t_char_code].size()){
        per++;
        cnt[t_char_code] = 0;
        prv = -1;
      }

      long now = posOfAlph[t_char_code].get(cnt[t_char_code++]);

      if(prv > now) per++;

      prv = now;
    }

    System.out.println(per == -1 ? -1 : per * (long)s_size + prv + 1L);
  }
}