Scanf.scanf "%d %d" (fun n k ->
    let xy = Array.init n (fun _ -> Scanf.scanf " %d %d" (fun x y -> x, y)) in
    let x, y = Array.fold_left (fun (xl, yl) (x, y) -> x :: xl, y :: yl) ([], []) xy in
    let x = Array.of_list x in
    let y = Array.of_list y in
    Array.sort compare x;
    Array.sort compare y;
    let rec loop1 i1 acc =
        let rec loop2 i2 x1 acc =
            let rec loop3 i3 x2 acc =
                let rec loop4 i4 y1 acc =
                    let count y2 =
                        Array.fold_left (fun acc (x, y) -> if x >= x1 && x <= x2 && y >= y1 && y <= y2 then acc + 1 else acc) 0 xy
                    in
                    if i4 >= n then acc else
                        let kk = count y.(i4) in
                        let acc = if kk >= k then min acc ((x2 - x1) * (y.(i4) - y1)) else acc  in
                        loop4 (i4 + 1) y1 acc
                in
                if i3 >= n - 1 then acc else loop3 (i3 + 1) x2 (loop4 (i3 + 1) y.(i3) acc)
            in
            if i2 >= n then acc else loop2 (i2 + 1) x1 (loop3 0 x.(i2) acc)
        in
        if i1 >= n - 1 then acc else loop1 (i1 + 1) (loop2 (i1 + 1) x.(i1) acc)
    in
    loop1 0 max_int |> Printf.printf "%d\n"
)