(Program
  (If
  { (Identifier)
  ->(Identifier) }
    (ExpressionStatements
    { (Identifier)
    ->(Identifier) })
    (If
    { (Identifier)
    ->(Identifier) }
      (ExpressionStatements
      {+(Identifier)+}
      {-(ExpressionStatements
          (Identifier))-})
      (If
      { (Identifier)
      ->(Identifier) }
        (ExpressionStatements
        { (Identifier)
        ->(Identifier) })
        (If
        { (Identifier)
        ->(Identifier) }
          (ExpressionStatements
          {+(Identifier)+}
          {-(ExpressionStatements
              (Identifier))-})
          (ExpressionStatements
          { (Identifier)
          ->(Identifier) }))))))