/-\        /-\        +-----+                 +-----+
      | S +******* R *********  FG *-----------------+  FG |
       \-/        \-/        |     |*                |     |
                             +--+--+  *              +--+--+
                                |      *                |
                                |       *               |
                                |        *              |
                                |        *              |
                  /-\        +--+--+     *           +--+--+
                 | R +------>+  FG +-----*-----------+  FG |
                  \-/        |     |     *           |     |
                             +--+--+    *            +--+--+
                                |      *                |
                                |     *                 |
                                |    *                  |
                                |***                    ^
                               / \                     / \    
                              /   \                   /   \   
                             /     \                 /     \ 
                            /       \               /       \ 
                           -----------             -----------
                             tree                     tree