d = gets.to_i
an = gets.split.map(&:to_i)
m = [1,0,1,0]

(an.size - 1).downto(3).each do |i|
    an[i-2] += an[i]
    an[i] = 0
end
an.pop while an.last == 0 and an.size > 1
puts an.size - 1
puts an.join(' ')