let n = read_int();;
let a = read_line() |> String.split_on_char ' ' |> List.map int_of_string |> List.sort compare |> Array.of_list;;
let inf = 1000000000;;
let dp = Array.make (n+1) inf;;
dp.(0) <- 0;;
for i = 0 to n do
  if i + 2 <= n then
    dp.(i+2) <- min dp.(i+2) (dp.(i) + a.(i+1) - a.(i));
  if i + 3 <= n then
    dp.(i+3) <- min dp.(i+3) (dp.(i) + a.(i+2) - a.(i));
done;;
print_int dp.(n);;
print_newline ();;