import java.util.Scanner

object Main {
  def main(args: Array[String]): Unit = {
    //nextLineとnextを同時に使ったら死ぬ
    val sc = new Scanner(System.in)

    val k = sc.nextInt()
    val a, b = sc.nextInt()

    var flag = false

    for (i <- a to b) {
      flag = flag || i % k == 0
    }

    val ans = if (flag) "OK" else "NG"

    println(ans)
  }

  @scala.annotation.tailrec
  def gcd(a: Int, b: Int): Int = {
    if (b == 0) a else gcd(b, a % b)
  }
  def debug(args: Any*): Unit = {
    Console.err.println(args.mkString(" "))
  }
}
