open Batteries
let n = read_int ()
let a = Array.init n @@ fun _ -> Scanf.scanf " %d" @@ fun b -> b

let _ =
  let rec loop i =
    if i * 2 > n then "YES" else(
    let ai = a.(i) in
    a.(i) <- min_int;
    if Array.mem ai a then "NO" else (
      a.(i) <- ai; loop (i+1)
    )
    )
  in loop 0 |> print_endline
