Substring of a Substring

Shefin gives you a string $S$ and you have to find a non-empty string $P$ such that: - $P$ is a substring of $S$. - **No** non-empty substring of $P$ is a **prefix** of $S$. - **No** non-empty substring of $P$ is a **suffix** of $S$. For all such possible strings, find the length of the **longest** string satisfying all the conditions. If no such string is possible, print $-1$. A string $A$ i