import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
      	int K = sc.nextInt();
      	int A = sc.nextInt();
      	int B = sc.nextInt();
      	for(int i=A;i<=B;i++){
        	if(i%K==0){
            	System.out.println("OK");
              	break;
            }
          	if(i==B && i%K!=0){
            	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