n = read_line.to_i
a = read_line.split.map(&.to_i).reverse
(n - 2).times do |i|
  k = a[i]
  a[i] -= k
  a[i + 2] += k
end
a.reverse!
if p = a.rindex {|i| i != 0 }
  a = a[0..p]
else
  a = [0]
end
puts a.size - 1, a.join(' ')