//STACK: T, x

ALGO (T) {
	st,sx=NIL;
	ct=T;
	lt=NIL;
	WHILE (ct!=NIL || lt!=NIL) DO
		IF (ct!=NIL) THEN
			ret=1;
			x=ct->key%2;
			st=PUSH(st,t);
			sx=PUSH(sx,x);
			ct=ct->dx;
		ELSE
			st=TOP(st);
			sx=TOP(sx);
			IF (lt!=ct->sx && ct->sx !=NIL) THEN
				a=elem;
				x=a+x;
				ct=ct->sx;
			ELSE
				IF (ct->sx=NIL) THEN
					a=elem;
					x=a+x;
					y=NIL;
				ELSE
					y=elem;
				ret=x*y*ct->key;
				st=POP(st);
				sx=POP(sx);
				elem=ret;
				lt=ct;
				ct=NIL;
	return elem;
}

//DUBBI se pushare di nuovo x quando faccio x=a+x;