let () =
  let x, y, n = Scanf.scanf "%d %d %d " (fun x y n -> x, y, n) in
  let a = Array.init n (fun _ -> Scanf.scanf "%d " (fun i -> i)) in
  let rec doit i =
    if i = n then true
    else
      if y * a.(i-1) > x * a.(i) then false
      else doit (i + 1) in
  print_endline (if doit 1 then "YES" else "NO")