tree(X,[X|Xs]-Xs).
tree(S,[X|Xs]-Zs) :- S0 is S - X, tree(S0,Xs-Ys), tree(S0,Ys-Zs).

okay(Xs,S,_) :- tree(S,Xs-[]).
okay(Xs,S,[Y|Ys]) :- S1 is S + Y, okay(Xs,S1,Ys).

determine(Xs,R) :- ( okay(Xs,0,Xs) -> R = yes ; R = no ).

getNumber(F,N0,N) :-
   get_code(F,C),
   ( C < 48 -> N = N0
   ; C > 57 -> N = N0
   ; N1 is N0 * 10 + C - 48, getNumber(F,N1,N)
   ).

getNumber(F,N) :- getNumber(F,0,N).

getNumbers(F,0,[]).
getNumbers(F,N,[X|Xs]) :- getNumber(F,X), N0 is N - 1, getNumbers(F,N0,Xs).

main(F) :-
   getNumber(F,N),
   ( N == 0 -> close(F)
   ; getNumbers(F,N,Xs), determine(Xs,R), format('~w~n',[R]), main(F)
   ).

main :-
   open('balance.in',read,F),
   main(F).