Interest Accumulation

For an array $A$ of size $N$, we define $f(A)$ in the following way: - Start with $score = 0$, and your hand is empty. - For each day $i = 1, 2, \ldots, N$, repeat the following steps in **this order**: - If your hand is empty, you may choose to pick up the current item with worth $A_i$, or you may choose not to. - If your hand contains an item, you may choose to sell the item and add