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: Accepted)

#n, q = gets.chomp.split(" ").map(&:to_i);
s = gets.chomp
t = gets.chomp

# validate
t.each_char do |c|
  unless s.include?(c)
    puts "-1"
    exit 0
  end
end

count = 0
s_index = 0
t_index = 0

while true do
  if count > s.size*(10**100)
    puts "-1"
    exit 0
  end
      if (t_index == (t.size))
    break
  end
  
  result = s.index(t[t_index], s_index)
  unless result.nil?
    count += (result + 1) - s_index
#    puts "c:" + count.to_s + ":" + t[t_index]
    s_index = (result + 1)
    t_index += 1
  else
    count += s.size - s_index
 #   puts "l:" + count.to_s + ":" + t[t_index]

    s_index = 0
  end
end

puts count