insert left a
insert right a
insert 2 b
insert 3 b
insert right a
insert left a
insert 3 a
insert 5 b
insert 5 b
insert left a
insert right b
insert 12 b 
insert 12 a
insert 8 b
insert right a
insert right b
insert right b
insert right b
insert right b
insert 12 a 
insert 21 b
delete 13
delete 14
insert left c
insert 2 c
insert 22 c
insert 22 c
insert right c
insert 25 c
insert 26 c