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