%dobetavan(N, R) :- N=1, R is 2, !.
%dobetavan(0, 1) :-  !.
dobetavan(0, 1).
dobetavan(N,R) :- N >0, W is N-1, dobetavan(W,Z), R is 2*Z.

sumto(1,1) :-!.
sumto(X,Y) :- W is X-1, sumto(W,Z), Y is Z+X.

alltwodigit :- myprint(10).
myprint(X) :- X < 100, write(X),nl, W is X+1, myprint(W).

alltwodigit2 :- myprint2(99).
myprint2(X) :- X > 9, W is X-1, myprint2(W), write(X),nl.
myprint2(9).