7
0 21 23 19 13 19 18 
21 0 10 8 12 6 7 
23 10 0 8 14 8 9 
19 8 8 0 10 4 5 
13 12 14 10 0 8 5 
19 6 8 4 8 0 3 
18 7 9 5 5 3 0