(Program
{+(Assignment
  {+(
    {+(Identifier)+}
    {+(Identifier)+})+}
  {+(
    {+(Integer)+}
    {+(Integer)+})+})+}
  (Assignment
  { (Identifier)
  ->(Identifier) }
    (Integer))
  (Assignment
  { (
    {-(Identifier)-}
    {-(Identifier)-})
  ->(Identifier) }
    (
      (Integer)
      (Integer)))
{-(Assignment
  {-(Identifier)-}
  {-(
    {-(Integer)-}
    {-(Integer)-})-})-})