a,b=gets.split.map(&:to_i)
aa=("%010d"%a).chars.map(&:to_i)
bb=("%010d"%b).chars.map(&:to_i)

class Fixnum
  def <(value)
    if self == 4 && value == 7
      return false
    elsif self == 7 && value == 4
      return true
    else
      super(value)
    end
  end
end

0.upto(9){|i|
  if aa[i] < bb[i]
    puts b
    break
  elsif bb[i] < aa[i]
    puts a
    break
  end
}