import kotlin.math.*
import java.util.*

fun main(args: Array<String>) {
  val k = readLine()!!.toInt()
  val (a, b) = readLine()!!.split(' ').map(String::toInt)
  for (i in a / k..b / k) {
    val ki = k * i
    if (a <= ki && ki <= b) {
      println("OK")
      return
    }
  }
  println("NG")
}
