7
0 28 28 22 17 21 22 
28 0 12 10 13 9 8 
28 12 0 10 17 11 10 
22 10 10 0 13 7 6 
17 13 17 13 0 10 7 
21 9 11 7 10 0 3 
22 8 10 6 7 3 0