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.Scanner;

public class Main 
{

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		
		String s = sc.next();
		String t = sc.next();
		
		int n = s.length();
		int m = t.length();
		
		int[] cnext = new int[26];
		int[][] next = new int[n][26];
		for(int i = 0; i < 26; i++)
			cnext[i]=-1;
		for(int i = 0; i < n; i++)
		{ //what chars exist?
			cnext[s.charAt(i)-'a'] = 0;
		}
		
		for(int i = n-1; i >= 0; i--)
		{
			int cid = s.charAt(i)-'a';
			
//			System.out.println(cid + " " + i);
			for(int j = 0; j < 26; j++)
			{
				next[i][j] = cnext[j];
			}
			cnext[cid] = i;
		}
//		System.out.println("test " + next[0][13]);
		
		long an = 0;
		int ch = 0; //char in s
		for(int i = 0; i < m; i++)
		{
//			System.out.println("i: " + i + ", ch " + ch);
			int tar = t.charAt(i)-'a';
			
			int got = next[ch][tar];
			if(tar == s.charAt(ch)-'a')
			{ //right here!
				an++;
				ch++;
				while(ch>=n)ch-=n;
			}
			else if(got == -1)
			{
//				System.out.println(" No " + i + "tar " + tar);
				System.out.println(-1);
				return;
			}
			else if(got == 0)
			{ //new s!
				an += n - ch;
				i--; //look again from 0!
//				System.out.println("MARK " + ch + " " + (char)('a'+tar) );
				ch = 0;
				
//				if(flag)return; //don't
			}
			else
			{
				an += got+1-ch;
				ch = got+1;
				while(ch>=n)ch-=n;
			}
			
		}
		
		System.out.println(an);

	}

}