Write a function solution that, given a string $S$ of length $N,$ returns the length of the shortest unique substring of $S,$ that is$,$ the length of the shortest word which occurs in $S$ exactly orfce.

Examples:

Given $S=$ "abaaba", the function should return $2.$ The shortest unique substring of $S$ is $"$aa$".$

Given $S="$zyzyzyz$",$ the function should return $5.$ The shortest unique substring of S is $"$yzyzy$".$ Note that there are shorter words, like $"$yzy$",$ occurrences of which overlap, but they still count as multiple occurrences.

Given $S=$ "aabbbabaaa", the function should

Search