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.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;
import java.util.TreeSet;

public class Main {

	public static void main(String args[])
	{
		Scanner scan=new Scanner(System.in);
		String s=scan.next();
		String t=scan.next();
		ArrayList<Integer>[] sad=new ArrayList[26];
		TreeSet<Integer> set[]=new TreeSet[26];
		int count1[]=new int[26];
		int count2[]=new int[26];
		for(int i=0;i<26;i++)
		{
			set[i]=new TreeSet<Integer>();
		}
		for(int i=0;i<s.length();i++)
		{
			count1[s.charAt(i)-'a']++;
			set[s.charAt(i)-'a'].add(i);
		}
		for(int i=0;i<t.length();i++) {
			count2[t.charAt(i)-'a']++;
		}
		for(int i=0;i<26;i++)
		{
			if(count1[i]==0 && count2[i]!=0)
			{
				System.out.println(-1);
				return;
			}
		}
		int pos=-1;
		long times=0;
		
		for(int i=0;i<t.length();i++)
		{
			int x=t.charAt(i)-'a';
//			int cur=set[x].higher(pos);
			if(set[x].last()<=pos) {
				times++;
				pos=set[x].first();
				
			}else {
				pos=set[x].higher(pos);
			}
//			System.out.print/ln(pos);
			
		}
		long ans=(s.length()*1L*times)+pos+1L;
		System.out.println(ans);
	
		
		
		
	}
}