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.util.Map.Entry;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] t = sc.next().toCharArray();
        char[] s = sc.next().toCharArray();
        HashMap<Character, ArrayList<Integer>> map = new HashMap<>();
        for (int i = 0; i < t.length; i++) {
            if(map.containsKey(t[i])) map.get(t[i]).add(i);
            else{
                map.put(t[i], new ArrayList<>());
                map.get(t[i]).add(i);
            }
        }
        HashMap<Character, int[]> tm = new HashMap<>();
        for(Entry<Character, ArrayList<Integer>> e : map.entrySet()){
            int[] tmp = new int[e.getValue().size()];
            for (int i = 0; i < e.getValue().size(); i++) {
                tmp[i] = e.getValue().get(i);
            }
            tm.put(e.getKey(), tmp);
        }
        long ans = 0L;
        boolean able = true;
        int pre = -1;
        int len = t.length;
        for (int i = 0; i < s.length; i++) {
            if(tm.get(s[i]) == null){
                able = false;
                break;
            }
            int[] tmp = tm.get(s[i]);
            int ins = Arrays.binarySearch(tmp, pre+1);
            if(ins < 0){
                ins = -(ins + 1);
                if(tmp.length-1 < ins){
                    ans += len - pre + tmp[0];
                    pre = tmp[0];
                }else{
                    ans += tmp[ins] - pre;
                    pre = tmp[ins];
                }
            }else{
                ans += tmp[ins] - pre;
                pre = tmp[ins];
            }
        }
        System.out.println(able ? ans : -1);
        sc.close();

    }

}