0

4619827353912518656

4619827353912518657

1

4619827353912518656

4619827353912518657

2

4619827353912518656

4619827353912518657

3

4619827353912518656

4619827353912518657

4

4619827353912518656

front concurrent concurrent

4619827353912518657

rear concurrent 4619827353912518656 5

4619827353912518657

front concurrent

4619827353912518656

rear concurrent concurrent 4619827353912518657