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

diamond(N) :-
	N1 is N*N,
	int_width(N1,W),
	Spaces1 is N*W,
	first(N,1,1,N,Spaces1,W),
	Start is N*(N - 1) + 2,
	Spaces2 is 2*W,
	last(N,Start,N,Spaces2,W).

first(0,_,_,_,_,_) :- !.
first(I,Start,Row,N,Spaces,W) :-
	I1 is I - 1,
	Start1 is Start + N,
	Row1 is Row + 1,
	Spaces1 is Spaces - W,
	writeN(Spaces,' '),
	writeline(Row,Start,N,W),
	first(I1,Start1,Row1,N,Spaces1,W).

last(1,_,_,_,_) :- !.
last(I,Start,N,Spaces,W) :-
	I1 is I - 1,
	Start1 is Start + 1,
	writeN(Spaces,' '),
	Spaces1 is Spaces + W,
	writeline(I1,Start,N,W),
	last(I1,Start1,N,Spaces1,W).

writeline(0,_,_,_) :- !, nl.
writeline(R,S,N,W) :-
	write_int(S,W),
	writeN(W,' '),
	S1 is S - N + 1,
	R1 is R - 1,
	writeline(R1,S1,N,W).