set-n-levels:5
insert:JFK:4
insert:ORD:9
insert:DFW:20
get-min-key
list-heap
insert:DEL:5
insert:LAX:6
get-min-key
get-max-level:JFK
get-max-level:ORD
get-max-level:DFW
get-max-level:DEL
get-max-level:LAX
list-heap
insert:CDG:7
insert:SFO:16
get-min-key
list-heap
insert:ATL:14
get-min-key
list-heap
insert:PEK:8
insert:BOS:11
get-min-key
list-heap
