let () = Scanf.scanf "%d %d\n" @@ fun n m ->
  let count = Array.make n true in
  for i = 0 to m - 1 do
    Scanf.scanf "%d %d\n" @@ fun a b ->
      count.(a - 1) <- not count.(a - 1);
      count.(b - 1) <- not count.(b - 1);
  done;
  print_endline @@
  if List.for_all (fun b -> b) @@ Array.to_list count then "YES" else "NO"
