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