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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.HashMap;
import java.util.Comparator;
import java.util.Collections;
import java.util.ArrayList;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        StringsofImpurity solver = new StringsofImpurity();
        solver.solve(1, in, out);
        out.close();
    }

    static class StringsofImpurity {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            String str = in.next();
            char[] s = str.toCharArray();
            char[] t = in.next().toCharArray();

            Map<Character, List<Integer>> map = new HashMap<>();
            for (int i = 0; i < s.length; i++) {
                List<Integer> list = map.getOrDefault(s[i], new ArrayList<>());
                list.add(i + 1);
                map.put(s[i], list);
            }

            for (char c : t) {
                if (!map.containsKey(c)) {
                    out.print(-1);
                    return;
                }
            }

            int pre = map.get(t[0]).get(0);
            long result = pre;

            for (int i = 1; i < t.length; i++) {
                List<Integer> pos = map.get(t[i]);
                int position = Collections.binarySearch(pos, pre, new LowerBoundComparator<>());
                int now;
                if (position < 0) {
                    position = ~position;
                    if (position == pos.size()) {
                        result += s.length;
                        now = pos.get(0);
                    } else {
                        now = pos.get(position);
                    }
                } else {
                    result += s.length;
                    now = pos.get(position);
                }

                result += (now - pre);
                pre = now;
            }

            out.print(result);

        }

        class LowerBoundComparator<T extends Comparable<? super T>> implements Comparator<T> {
            public int compare(T x, T y) {
                return (x.compareTo(y) >= 0) ? 1 : -1;
            }

        }

    }
}