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.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		char[] s = sc.next().toCharArray();
		char[] t = sc.next().toCharArray();
		int N = s.length;
		int M = t.length;

		int[][] nextIndex = new int[26][N+1];
		for(int i=0; i<26; i++)
			Arrays.fill(nextIndex[i], -1);
		
		for(int i=N-1; i>=0; i--) {
			for(int j=0; j<26; j++) {
				nextIndex[j][i] = s[i]=='a'+j ? i : nextIndex[j][i+1];
			}
		}
		
		long ans = 0;
		int cur = 0;
		for(int i=0; i<M; i++) {
			if(nextIndex[t[i]-'a'][cur] < 0 ) {
				if(nextIndex[t[i]-'a'][0] < 0) {
					System.out.println(-1);
					sc.close();
					return;
				} else {
					ans += nextIndex[t[i]-'a'][0]+1 +N - cur;
					cur = nextIndex[t[i]-'a'][0]+1;
				}
			} else {
				ans += nextIndex[t[i]-'a'][cur]+1 - cur;
				cur = nextIndex[t[i]-'a'][cur]+1;
			}
		}
		
		System.out.println(ans);
		
		sc.close();
	}
}