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