In preparation for back to school night, the school administration has planned to replace the tile in the cafeteria. They would like to have a checkerboard pattern of tiles two rows wide as a surround for the tables and serving carts. The contractor that was hired to lay the tile is trying to generalize a way to calculate the number of colored tiles with dimensions s x s. Find an expression for the number of colored border tiles needed for any s x s square center.​