Sort the Array

Given an array $A$ of size $N$. You can do the following operation on the array: - Pick any $2$ **distinct** indices $i$ and $j$ such that $A_i=A_j$; - Change all the elements between the indices $i$ and $j$ to $A_i$, i.e, for all $k$ $(i \leq k \leq j)$, set $A_k=A_i$. Find the **minimum** number of operations required to **sort** the array in non-decreasing order. If it is not possible to sor