% 20-queens:
% 9 13 2 8 11 20 10 6 19 15 18 12 7 16 4 17 14 5 3 1 
%
q = [9, 13, 2, 8, 11, 20, 10, 6, 19, 15, 18, 12, 7, 16, 4, 17, 14, 5, 3, 1];
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