A tiled floor of a room has dimensions in meters of m x m.
The dimensions in meters of the tiles used are n x n.
All tiles used are green tiles except diagonal tiles which are red.
After some years some green tiles are replaced by red tiles to form an alternate red and green tile pattern.
How many green tiles are removed?
(m is divisible by n, m is not equal to n, and the total number of tiles is odd).