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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
class Program
{
	static void Main(string[] args)
	{
		string s = Console.ReadLine();
		string t = Console.ReadLine();
		string aaa = "abcdefghijklmnopqrstuvwxyz";
		var list = new List<int>[26];
      	for(var i=0;i<26;i++){
          list[i] = new List<int>();
        }
		for(var i=0;i<s.Length;i++){
			int a1 = aaa.IndexOf(s.Substring(i,1));
			list[a1].Add(i);
		}
		long ans = 0;
		for(var i=0;i<t.Length;i++){
			int a1 = aaa.IndexOf(t.Substring(i,1));
			if(list[a1].Count==0){
				ans = -1;
				break;
			}
		}
		if(ans!=-1){
			int a1 = aaa.IndexOf(t.Substring(0,1));
			int b1 = list[a1][list[a1].Count-1];
			for(var i=1;i<t.Length;i++){
				int a2 = aaa.IndexOf(t.Substring(i,1));
				int min = 0;
				int max = list[a2].Count;
				while(min<max){
					int m = (min+max)/2;
					if(list[a2][m]>b1){
						max = m;
					} else {
						min = m+1;
					}
				}
				if(min==list[a2].Count){
					min = 0;
					ans++;
				}
				b1 = list[a2][min];
			}
          	ans = ans * s.Length + b1+1;
		}
		Console.WriteLine(ans);
	}
}