3531. Count Covered Buildings

You are given a positive integer n, representing an n x n city. You are also given a 2D grid buildings, where buildings[i] = [x, y] denotes a unique building located at coordinates [x, y]. A building is covered if there is at least one building in all four directions: left, right, above, and below. Return the number of covered buildings. Example 1: Input: n = 3, buildings = [[1,2],[2,2],[3,2