func main() {
  let k = Int(readLine()!)!
  let ab = readLine()!.split(separator: " ").map { Int($0)! }
  let (a, b) = (ab[0], ab[1])

  for i in a...b {
    if i % k == 0 {
      print("OK")
      return
    }
  }

  print("NG")
  return
}

main()
