Problem:
You have a grid of squares. You write a number in each square as follows: you write from left to right across the top row, then across the second row, and so on, ending with in the bottom right square. You then write a second number in each square, writing in the first column (from top to bottom), then in the second column, and so forth.
When this process is finished, how many squares will have the property that their two numbers sum to ?