let read_int () = Scanf.scanf " %d" (fun x -> x);;

let n = read_int ();;
let a = Array.init n (fun _ -> read_int ());;
Array.sort compare a;;

let all = ref true;;
for i = 0 to n - 2 do
  if a.(i) + 1 >= a.(i + 1) then
    all := false
done;;

print_endline (if !all then "1" else "2");;