Suppose the riceballs are numbered from ~1~ to ~N~, with riceball ~i~ having size ~A[i]~. Define a boolean function ~f(i, j)~ to return ~1~ if the riceballs in the range ~[i, j]~ can all be combined into a single riceball, or ~0~ otherwise. The final answer to the problem is:

$$\displaystyle \max_{1 \le i \le j \le N} f(i, j) \cdot \sum_{k=i}^j A[k]$$

Remember that no matter how you combine riceballs in an interval, after they are combined the size will always be the same.

We have the following recurrence:

$$\displaystyle f(i, j) = \begin{cases} 1 & \text{if } i \ge j \\ \max_{i \le a \le b \le j} f(i, a) \cdot f(a+1, b-1) \cdot f(b, j) & \text{otherwise, where } \sum_{k=i}^a A[k] = \sum_{\ell=b}^j A[\ell] \end{cases}$$

To speed this up, notice that for every ~a~ there is at most one ~b~ that satisfies the size restriction, and when ~a~ increases, ~b~ decreases, so all valid pairs may be found with a two-pointers algorithm.

Complexity: ~\mathcal{O}(N^3)~