import java.util.Scanner;
 
public class Main { //クラス名はMain
    public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
      int K = in.nextInt();
      int A = in.nextInt();
      int B = in.nextInt();
     
       if ((B/K - A/K >=1)||(B%K==0)||(A%K==0))
            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