Count Distinct Squares

You are provided with a list of N integer coordinates that represent the bottom-left corners of squares with a side length of 1. Your task is to count how many distinct unit squares are covered by at least one of the squares. The input begins with an integer N followed by N pairs of integers representing the coordinates. Output the total count of distinct unit squares covered. Example: Input: 5 0 0 0 1 1 0 1 1 1 2 Output: 6