Substring Matching

You are given a string $T$ and $n$ (not necessarily distinct) strings $S_1, S_2, \ldots, S_n$. What is the maximum length of a substring of $T$ that can be formed by choosing some strings from $S_1, S_2, \ldots, S_n$, and concatenating them in some non decreasing order of length. Please note that there might be multiple non decreasing orders possible. Formally, Consider all the strings $Y$ that