class Lista
	def initialize
		@beginning = @tail nil
	end
	
	def add (valor)
		nodo = Nodo.new(valor)
		
		@beginning = nodo if @beggining.nil?
		
		@tail.next = node unless @tail.nil?
		@tail = node
	end
end

class Nodo
	def initialize(value)
		@valor = valor
		@next = nil
	end

	def next
		@next
	end
	
	def next=(valor)
		@next = valor
	end
end