import java.util.Scanner
import scala.io.StdIn._

object Main extends App {

  val k = readInt()
  val Array(a, b) = readLine().split(" ").map(_.toInt)


  def solve(): String = {
    (a to b).foreach(i => if(i % k == 0) return "OK")
    "NG"
  }

  println(solve())

}

