class Creature
    attr_accessor :kind

    def initialize(kind)
        @kind = kind
    end
end

class Human
    extend Creature
    attr_accessor :firstName

    def initialize(firstName)
        @firstName = firstName
    end
end

class Animal
    extend Creature
    attr_accessor :nickname

    def initialize(nickname)
        @nickname = nickname
    end
end

class Union
    attr_accessor :union, :intersection, :discriminator

    def initialize(union, intersection, discriminator)
        @union = union
        @intersection = intersection
        @discriminator = discriminator
    end
end