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.BitSet;
import java.util.Scanner;

class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String m = sc.nextLine().trim();
        String c = sc.nextLine().trim();

        char[] chars = (m + m).toCharArray();
        BitSet[] indexes = new BitSet[26];
        for (int i = 0; i < chars.length; i++) {
            int ch = chars[i] - 'a';
            BitSet index = indexes[ch];
            if (index == null) index = indexes[ch] = new BitSet(chars.length);
            index.set(i);
        }

        long start = 0;
        int ptr = -1;
        for (char ch : c.toCharArray()) {
            BitSet index = indexes[ch - 'a'];
            if (index == null) {
                System.out.println(-1);
                return;
            }

            ptr = index.nextSetBit(ptr + 1);
            if (ptr >= m.length()){
                ptr -= m.length();
                start += m.length();
            }
        }

        System.out.println(start + ptr + 1);
    }
}