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.io.ByteArrayInputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeSet;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        main1(sc);
    }

    public static void main1(Scanner sc) {

    	char[] base = sc.next().toCharArray();
    	char[] target = sc.next().toCharArray();

    	Map<Character, TreeSet<Integer>> posIndex = new HashMap<Character, TreeSet<Integer>>();

    	for (int i = 0; i < base.length; i++) {
    		char c = base[i];
    		TreeSet<Integer> t = posIndex.get(c);

    		if (t == null) {
    			t = new TreeSet<Integer>();
    			posIndex.put(c, t);
    		}

    		t.add(i);
    	}

    	long pos = 1;
    	int prevPos = -1;

    	for (int i = 0; i < target.length; i++) {
    		char c = target[i];

    		TreeSet<Integer> idx = posIndex.get(c);
    		if (idx == null) {
    			System.out.println("-1");
    			return;
    		}

    		Integer next = idx.higher(prevPos);

    		if (next == null) {
    			next = idx.first();

    			pos += base.length - 1 - prevPos + next + 1;
    			prevPos = next;

    		} else {
    			if (prevPos < 0) {
    				prevPos = 0;
    			}
    			pos += next - prevPos;
    			prevPos = next;
    		}
    	}

    	System.out.println(pos);

    }
	public static void maina(String[] args) throws Exception {
		String in1 = "contest\r\n" +
				"son";

		String in2 = "contest\r\n" +
				"programming";

		String in3 = "contest\r\n" +
				"sentence";

		Scanner sc = new Scanner(new ByteArrayInputStream(in1.getBytes()));
		main1(sc);

		sc = new Scanner(new ByteArrayInputStream(in2.getBytes()));
		main1(sc);

		sc = new Scanner(new ByteArrayInputStream(in3.getBytes()));
		main1(sc);
	}
}