Positive array

​A `1`-indexed array is called *positive* if every element of the array is greater than or equal to the index on which it lies. Formally, an array $B$ of size $M$ is called positive if $B_i \ge i$ for each $1\le i \le M$. For example, the arrays $[1], [2, 2], [3, 2, 4, 4]$ are positive while the arrays $[2, 1], [3, 1, 2]$ are not positive. You are given an array $A$ containing $N$ integers. You