Well, If I understand you well,a choice N is in row R and column CR = floorC = N mod 3example: if N=5 then R=floor(7/3)=2 and C=5 mod 3=2
a choice N is in row R and column C
R = floorC = N mod 3
example: if N=5 then R=floor(7/3)=2 and C=5 mod 3=2