What I simply want to do is, seeing friends in the page "Friends Standings" — how can I add somebody to my friends?

Hi! I'm searching for a data structure, which efficiently offers the following two operations. On points in a 2D plane.

1) Add a point to the structure.

2) Count the number of points in a given rectangle, which is paralell to x and y axis.

Could anyone tell me if such data structure exists, or even better give me a linik to a simmilar problem on.