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