Deletion Sort

You are given an array $A$ of length $N$. Let $F(L,R)$ be the array you get from $A$ after removing all occurrences of $A_L, A_{L+1}, \dots , A_R$. In other words, for each value in $A$ between the indices $L$ and $R$, you delete every occurrence of that value, including occurrences outside the range $[L, R]$. A pair $(L,R)$ is called good if $1\le L\le R\le N$ and $F(L, R)$ is sorted in no