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 = {
    val largest = (b/k) * k
    if(largest >= a) "OK" else "NG"
  }

  println(solve())

}

