// We Love Golf

func main() {
    let k = Int(readLine()!)!
    let ab = readLine()!.split(separator: " ").map{Int($0)!}
    if (ab[0] / k != ab[1] / k) || ab[0] % k == 0 {
        print("OK")
    } else {
        print("NG")
    }
}

main()