Problem:
Score : 100 points

Problem Statement

You are given strings s and t.
Find one longest string that is a subsequence of both s and t.

Notes

A subsequence of a string x is the string obtained by removing zero or more characters from x and concatenating the remaining characters without changing the order.

Constraints

s and t are strings consisting of lowercase English letters.

1 \leq |s|, |t| \leq 3000

Input

Input is given from Standard Input in the following format:

s
t

Output

Print one longest string that is a subsequence of both s and t.
If there are multiple such strings, any of them will be accepted.

Sample Input 1

axyb
abyxb

Sample Output 1

axb

The answer is axb or ayb; either will be accepted.

Sample Input 2

aa
xayaz

Sample Output 2

aa

Sample Input 3

a
z

Sample Output 3

The answer is (an empty string).

Sample Input 4

abracadabra
avadakedavra

Sample Output 4

aaadara

Solution in Ruby (2.3.3) (judge verdict: Time Limit Exceeded)

s = gets
t = gets
ret = ''
[0,1].repeated_permutation(s.chars.size).sort_by {|a| a.count {|i| i == 1} }.reverse.each do |arr|
  subchars = arr.map.with_index do |a,i|
    a == 0 ? nil : s.chars[i]
  end.compact
  next unless subchars.all? {|c| t.chars.include?(c)}
  tmp = t.chars.dup
  flg = true
  subchars.each do |c|
    if i = tmp.index(c)
      tmp = tmp[(i+1)..-1]
    else
      flg = false
      break
    end
  end
  ret = subchars.join and break if flg
end
puts ret