7
0 31 28 22 17 21 21 
31 0 15 13 16 12 12 
28 15 0 10 19 11 11 
22 13 10 0 15 7 7 
17 16 19 15 0 12 8 
21 12 11 7 12 0 4 
21 12 11 7 8 4 0