import java.util.Scanner;

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 s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			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