---| 15 |-----------------------------------------

20    -----------------------|
      |                      |
      |                      |
      |                      |
      |  \              /    |
      |    \         /       |
      |  0              0    |
      |                      |
      |                      |
10    -         &            |
      |  _              _    |
      |                      |
      |    \         /       |
      |       \ _  /         |
      |                      |
      |                      |
      |                      |
1     ----------|------------|
     1         5            10