I need help with understand the code for the flippingmatrix problem. The goal of the game is to maximize the sum of the elements in the 2x2 submatrix located in the upper-left quadrant of the matrix. The relevant code snippet ends at return max_total.

Can someone walk me through the line of code, for example why do we have /2 at the end of n=int(len(matrix)/2)? and I dont understand why in max_s we have (2*n-1)