1: (7)
2: (3, 6)
3: (2, 7)
4: (10)
5: (9, 10)
6: (2, 7, 11)
7: (1, 3, 6, 12)
8: (13)
9: (5, 13, 14)
10: (4, 5, 15)
11: (6)
12: (7)
13: (8, 9)
14: (9, 15)
15: (10, 14)

The distance from 1 to 12 is 2
A shortest 1-12 path is: (1, 7, 12)

The distance from 1 to 15 is infinity
No 1-15 path exists

The distance from 4 to 8 is 5
A shortest 4-8 path is: (4, 10, 5, 9, 13, 8)

The distance from 9 to 6 is infinity
No 9-6 path exists

The distance from 15 to 8 is 4
A shortest 15-8 path is: (15, 14, 9, 13, 8)