          |
|        (c r)   /        ((c) (r))        \    (c (r))     |
|          (r)  o             c             o  ((c, r))     |
|               |\           / \           /|               |
|               | \         /   \         / |               |
|               |  \       /     \       /  |               |
|               |   \     /       \     /   |               |
|               |    \   /         \   /    |               |
|               |     \ /           \ /     |               |
|   