7
0 21 21 19 13 17 17 
21 0 12 8 12 8 8 
21 12 0 6 14 8 8 
19 8 6 0 10 4 4 
13 12 14 10 0 10 6 
17 8 8 4 10 0 4 
17 8 8 4 6 4 0