$v$

$t_{v,\text{start}}$

$t_{v,end}$

$v$

$t_{v,\text{start}}$

$t_{v,end}$

1

8:30

14:00

7

13:30

18:00

2

15:30

18:30

8

7:00

14:00

3

9:00

13:00

9

14:30

18:00

4

14:30

18:00

10

8:00

12:00

5

8:30

11:00

11

12:00

15:00

6

18:00

20:00