import scala.io.StdIn.readLine
import scala.io.StdIn.readInt

object Main extends App {
    val k = readLine.toInt
    val ab = readLine.split(" ").map(x => x.toInt);
    val a = ab(0)
    val b = ab(1)
    if((a-1)/k < b/k) print("OK");
    else print("NG")

}