Ok, crux of it goes like this: the number of parameters you have for a single dp state, multiply their worst cast limit together. Plus if you have inside loops inside the dp state, those factor in too. You have 3 parameters here, namely 'ind', 'tot' and 'term' whose maximum values can be 300. So we get 300^3 by multiplying them. You also have a loop going on inside the dp state which adds an iteration of 300 at most. That's how you get 300^4 or O(N^4) complexity.