               /     |        |
|        |   *  \                 /  *   |        |
|        X   *   Y               Y   *   Z        |
|         \  *   |               |   *  /         |
|          \ G   |               |   H'/          |
|           \    |               |    /           |
|            \   |               |   /            |
|             \  |               |  /             |
|              \ |               | /              |
|               \|               |/               |
|           