For n squares. Each square is determined by the coordinates of the bottom-left point and the length of each edge. The i th square has the coordinates of the bottom-left point is $(x_i, y_i)$ and the edge length $l$. No $2$ squares have the same bottom-left coordinates. A square contains a point when that point is inside or on the edge of that square. Calling function $f(X)$ is the number of squares in the set of n squares that contain point X.
For $m$ points $P_j(1\le j\le m)$. Find the maximum value of $f(P_j)$ with $1\le j\le m$. No 2 points have the same coordinates.
For example: We have 2 squares have bottom-left coordinates respectively $(1;1),(3;1)$, $1$ points $P_1$ has coordinates $(3;2)$ and $l=2$. The result of problem is $2$. Because $f(P_1)=2$.
This is my try: I thought, this problem is relevant to convex hull and rescursive form, but I can't do it.