White and Black

You are given chessboard with rows numbered from $1$ to $n$ from bottom to top and columns are numbered from $1$ to $m$ from left to right. Every cell on the chessboard can be represented as $(x,y)$ where $x$ is the column number and $y$ is the row number. The $(1,1)$ coordinate of the chessboard is white. The coordinate pair $(a,b,c,d)$ represents a rectangle formed where $(a,b)$ is the bott