lib C
  fun strtoll(s : UInt8*, p : UInt8**, b : Int32) : Int64
end

class String
  def to_i64
    C.strtoll(self, nil, 10)
  end
end

n = read_line.to_i
b = (1..n).map { read_line.to_i64 }
a = Array.new(n + 1, 0i64)
n.times { |i| a[i + 1] = i.even? ? b[i] - a[i] : a[i] - b[i] }

need = (0..n).select { |i| i % 4 == 0 || i % 4 == 3 }.max_of { |i|
  {1i64 - a[i], 0i64}.max
}
can = (0..n).select { |i| i % 4 == 1 || i % 4 == 2 }.min_of { |i|
  {a[i] - 1i64, 0i64}.max
}

if need <= can
  (0..n).each do |i|
    if i % 4 == 0 || i % 4 == 3
      a[i] += need
    else
      a[i] -= need
    end
  end
  puts n + 1, a.join("\n")
else
  puts -1
end