Subset sum problem with a complication

I have a sorted list of numbers. I know they can be divided into two parts. I also know the sum of those 2 parts. I want to know what these subsets are. How can i find them? The size of my list can be ~ 10^6. The sum of my subsets can be ~ 10^24. Is there a better way to find my subset with a time complexity of O(n*sum) or O(n^2 logn) or is it not possible?