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 Ruby (2.3.3) (judge verdict: Runtime Error)

def to_hash_key(a)
  a.ord - 'a'.ord
end

s = gets.chomp
t = gets.chomp

hash = Array.new(26) { Array.new }
hash2 = Array.new(26) { Array.new }
0.upto(s.size - 1) do |i|
  hash2[to_hash_key(s[i])].push(i + 1)
end

0.upto(25) do |i|
  if hash2[i].empty?
    hash[i] = [nil] * (s.size + 1)
    next
  end
  hash2[i].unshift(0)
  0.upto(hash2[i].size - 2) { |j| hash[i] += [hash2[i][j + 1]] * (hash2[i][j + 1] - hash2[i][j]) }
  hash[i] += [hash2[i][1]] * (hash2.size - hash2[i][-1]) 
end

ans = 0
current = 0
t.chars.each do |c|
  key = to_hash_key(c)
  next_pos = hash[key][current]
  if next_pos.nil?
    puts '-1'
    exit 
  end
  ans +=  if current < next_pos
            next_pos - current
          else
            s.size + next_pos - current
          end
  current = next_pos
end

puts ans