Add:station 2
Add:queue
Add:station 1
Add:queue
Top:queue
Remove:queue
Remove:station
Queue
Size:queue
Train
Remove:queue
Remove:station
Queue
Size:queue
Train
Add:station 4
Add:queue
Add:station 3
Add:queue
Top:queue
Remove:queue
Remove:station
Queue
Size:queue
Train
Remove:queue
Remove:station
Add:queue
Queue
Size:queue
Train