Optimization of a matrix depending on slope and distance

I'm a beginner optimization user and I haven't used it much.

I would like to know if you would know how to perform my optimization problem, I have a 1000X1000 square mesh matrix (each point is one meter away from the next ) with altitude values of the points. I have to select 20 points that (attachment matrix .mat):

• Are as close together as possible and the general shape is as close to a rectangle (if possible).
• Minimum Slope
• Distance in Y betwen points=> 1meter
• Distance in X betwen points=> 2 meters

Thank you very much for your help.

[darova]

Did you try something? Any idea?