require 'thread'

require 'queue'

class Stack

# Initialize your data structure here.

def initialize

@quque1 = Queue.new

@queue2 = Queue.new

@top_element = nil

end

# @param {Integer} x

# @return {void}

def push(x)

if self.empty

@queue1.push x

return

end

if @queue1.empty?

@queue1.push x

until @queue2.empty?

@quque1.push @queue2.pop

end

else

@queue2.push x

until @queue1.empty?

@queue2.push @queue1.pop

end

end

end

# @return {void}

def pop

if @top_element.nil?

if @queue1.empty?

@queue2.pop

else

@queue1.pop

end

else

@top_element = nil

end

end

# @return {Integer}

def top

if @top_element.nil?

@top_element = @quque1.empty? ? @queue2.pop : @queue1.pop

end

@top_element

end

# @return {Boolean}

def empty

@quque1.empty? and @queue2.empty?

end

end

stack = Stack.new

stack.push 1

puts stack.top

puts stack.top