insert 8
8
insert 6
6
  -
  8
insert 7
7
  6
  8
insert 5
5
  -
  6
    -
    7
      -
      8
insert 3
3
  -
  5
    -
    6
      -
      7
        -
        8
insert 0
0
  -
  3
    -
    5
      -
      6
        -
        7
          -
          8
insert 9
9
  8
    0
      -
      5
        3
        7
          6
          -
    -
  -
lookup 6
6
  0
    -
    5
      3
      -
  9
    8
      7
      -
    -
delete 5
3
  0
  6
    -
    9
      8
        7
        -
      -