import java.io.*;
import java.util.*;

public class Main {
        public static void main(String[] args) {
                Scanner scan = new Scanner(System.in);

                int K = scan.nextInt();
                int A = scan.nextInt();
                int B = scan.nextInt();

                int syou = A/K;
                int hantei = K * syou;

                while (true) {
                        if (hantei > B) {
                                System.out.println("NG");
                                break;
                        }
                        if (hantei >= A) {
                                System.out.println("OK");
                                break;
                        }
                        hantei += K;
                }
        }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz