Trying out every possibility is too slow because of the size of the number ~N~. It is important to notice that the number of possible summands cannot be very large. More precisely, the number of summands will not be greater than ~\sqrt{2N}~, because otherwise their sum would exceed ~N~ (see this for yourself). Therefore, we have enough time to iterate over all possible ~K~ (where ~K~ is the number of consecutive summands), and for each of them search for the corresponding summands, i.e., the first and the last number – we can do this either mathematically (the formula is easily derived), or by binary search.