7
0 21 21 17 12 18 17 
21 0 10 10 13 7 8 
21 10 0 8 13 7 8 
17 10 8 0 11 5 6 
12 13 13 11 0 8 5 
18 7 7 5 8 0 3 
17 8 8 6 5 3 0