Team Trees

You are given a string $S$ with length $N$. You should find two non-intersecting substrings of $S$ such that the second one is a substring of the first one and the product of these substrings' lengths is the maximum possible. More formally, let's denote a contiguous substring $S_l, S_{l+1}, \ldots, S_r$ by $S[l, r]$; you should find integers $l_1$, $r_1$, $l_2$ and $r_2$ which satisfy these four c