import scala.io.StdIn._
import scala.util.control.Breaks
object Main extends App {
  val k = readLine.trim.split(' ').map(_.toInt).apply(0)
  val Array(a, b) = readLine.trim.split(' ').map(_.toInt)

  val break = new Breaks
  var is_find = false
  break.breakable{
    (a/k to b/k+1).foreach(i => {
      val ki = k*i
      if(a <= ki && ki <= b){
        is_find = true
        break.break()
      }
    })
  }

  println(if(is_find) "OK" else "NG")
}
