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% c(N,C) - C is a checkerboard of size N, if .. t(0,1). t(1,0). r([],_). r([H|T],H):-t(H,I),r(T,I). f([],_,_). f([H|T],N,B):-length(H,N),r(H,B),t(B,D),f(T,N,D). c(N,C):-length(C,N),f(C,N,1).