let k = Scanf.sscanf (read_line ()) "%d" @@ fun k -> k
let (a, b) = Scanf.sscanf (read_line ()) "%d %d" @@ fun a b -> (a, b)

let () =
  for i = a to b do
    if i mod k = 0 then begin 
      print_endline "OK";
      exit 0
    end
  done;
  print_endline "NO"
