:- use_module(contestlib,[writeN/2]).

stop(N) :-
	first_last_line(N),
	slope(N - 2,N - 2,N,-1),
	vertical(N//2,3*N - 4),
	mid(3*N - 6),
	vertical(N//2,3*N - 4),
	slope(N - 2,1,3*N - 6,1),
	first_last_line(N).

first_last_line(N) :-
	N1 is N - 1,
	space(N1),
	red(N),
	nl.

slope(M,SpaceBefore,SpaceMiddle,I) :-
	( M > 0 ->
	    space(SpaceBefore), red(1), space(SpaceMiddle), red(1), nl,
	    M1 is M - 1,
	    SpaceBefore1 is SpaceBefore + I,
	    SpaceMiddle1 is SpaceMiddle - I - I,
	    slope(M1,SpaceBefore1,SpaceMiddle1,I)
	;
	    true
	).

mid(N) :- red(1), space(1), white(N), space(1), red(1), nl.

vertical(N,Space) :-
	( N > 0 ->
	    red(1), space(Space), red(1), nl,
	    N1 is N - 1,
	    vertical(N1,Space)
	;
	    true
	).

red(N) :- writeN(N,'R').

space(N) :- writeN(N,' ').

white(N) :- writeN(N,'W').