7
0 20 18 15 11 12 12 
20 0 12 9 11 10 10 
18 12 0 7 13 8 8 
15 9 7 0 8 3 3 
11 11 13 8 0 7 5 
12 10 8 3 7 0 2 
12 10 8 3 5 2 0