20
12 11 13 15 16 17 14 19 18 20 
18 20 12 17 11 19 16 15 13 14 
14 13 18 19 11 17 20 12 16 15 
19 20 11 16 18 17 12 15 14 13 
18 15 12 20 11 14 17 13 19 16 
15 12 20 14 13 17 18 19 16 11 
20 12 14 11 16 13 19 18 17 15 
11 18 12 17 20 16 15 19 13 14 
11 13 19 12 16 14 20 18 15 17 
20 16 17 15 12 19 13 11 14 18 
8 4 5 1 10 2 3 6 9 7 
8 4 1 6 10 9 2 3 7 5 
9 10 7 1 5 6 4 2 3 8 
6 9 1 7 8 4 3 2 10 5 
3 10 6 7 5 2 8 4 9 1 
7 2 6 9 1 10 4 8 5 3 
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3 4 8 9 1 10 5 7 6 2 
8 9 4 1 7 3 2 10 5 6 
10 1 4 5 7 8 9 6 3 2 
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forbidden 9 11
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forbidden 10 19