You are given an integer n representing an n $ imes$ n grid and a $2 ext{D}$ integer array buildings, where buildings[i] = [x, y] denotes the coordinates of a building on the grid.

A building at [x, y] is considered covered if there is at least one building in all four directions:

• Above: a building at [x', y] with $x' < x$

• Below: a building at [x', y] with $x' > x$

• Left: a building at [x, y'] with $y' < y$

• Right: a building at [x, y'] with $y' > y$

Return the total number of covered buildings.

Constraints:

• $2 \leq$ n $\leq 10^5$

• $1 \leq$ buildings.length $\leq 10^5$

• buildings[i] = [x, y]

• $1 \leq x, y \leq$ n

• All coordinates of buildings are unique.

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.