class Node
	attr_accessor :value,:next_node
	def initialize(val,nxt)
		@value = val
		@next_node = nxt
	end
end
class Stack
	attr_accessor :data
	def initialize(d=nil)
		@data = d
	end
	def push(node)
		node.next_node = @data
		@data = node
	end
	def pop
		return @data if not @data
		node = @data
		@data = @data.next_node
		return node
	end
end
def reverse_nodes(stack)
	return stack.data	
end
def print_values(node)
	if node
		print "#{node.value} --> "
		print_values(node.next_node)
	else
		print "nil\n"
	end
end
s = Stack.new
ll = Node.new(1,Node.new(2,Node.new(3,nil)))

print_values(ll)

node = ll
while node
	s.push(node.clone) # because ruby passes by reference!
	node = node.next_node
end

print_values(reverse_nodes(s))