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.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class Main {
	static private class Pat {
		List<Integer> of = new ArrayList<Integer>();;
	}

	static Pat[] pat = new Pat[26];

	public static void main(String[] args) {
		Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		String s = in.next();
		String t = in.next();
		for (int i = 0; i < pat.length; i++)
			pat[i] = new Pat();
		getPat(s);
		System.out.println(solve(t, s.length()));
	}

	private static long solve(String t, int slen) {
		long ans = 0;
		int d = 0;
		for (int i = 0; i < t.length(); i++) {
			int dn = searchPat(t.charAt(i), d);
			if (dn == 0)
				return -1;
			if (dn < 0) {
				ans += slen;
				d = 0;
				i--;
			} else
				d = dn;
		}
		return ans + d;
	}

	private static int searchPat(char c, int d) {
		int p = c - 'a';
		if (pat[p].of.isEmpty())
			return 0;
		int end = pat[p].of.size();
		if (pat[p].of.get(end - 1) <= d)
			return -1;
		return searchBin(p, d, 0, end);
	}

	private static int searchBin(int p, int d, int s, int e) {
		if (s == e)
			return pat[p].of.get(s);
		int m = (s + e) / 2;
		if (pat[p].of.get(m) > d)
			return searchBin(p, d, s, m);
		else
			return searchBin(p, d, m + 1, e);
	}

	private static void getPat(String s) {
		for (int i = 0; i < s.length(); i++)
			pat[s.charAt(i) - 'a'].of.add(i + 1);
	}
}