s = gets
t = gets

d = Array.new(s.length + 1){ Array.new(t.length + 1){ [0, ''] }}

(1..(s.length)).each do |i|
  (1..(t.length)).each do |j|
    d[i][j] = s[i-1] == t[j-1] ? [d[i-1][j-1][0] + 1, d[i-1][j-1][1] + s[i-1]] : d[i-1][j][0] > d[i][j-1][0] ? d[i-1][j] : d[i][j-1]
  end
end

puts d[-1][-1][1]