import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
        final int k = s.nextInt();
        int a = s.nextInt();
        final int b = s.nextInt();

        boolean okFlg = false;
        while (a <= b) {
            if (a % k == 0) {
                okFlg = true;
                break;
            }
            a++;
        }
        if (okFlg) {
            System.out.println("OK");
        } else {
            System.out.println("NG");
        }
  }
}
/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