import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
		// TODO Auto-generated method stub
          Scanner scn= new Scanner(System.in);
          int k = scn.nextInt();
          int a=scn.nextInt();
          int b=scn.nextInt();
          if(a%k==0 || b%k==0 || (b/k-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