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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}

} import java.util.Scanner; Scanner java.util 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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}

} 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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	} main {
		Scanner scan = new Scanner(System.in);
		int K = scan.nextInt();
		int A = scan.nextInt();
		int B = scan.nextInt();

		int max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int K = scan.nextInt(); K scan.nextInt() scan.nextInt scan int A = scan.nextInt(); A scan.nextInt() scan.nextInt scan int B = scan.nextInt(); B scan.nextInt() scan.nextInt scan int max = (B / K) * K; max (B / K) * K (B / K) B K K if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		} max >= A max A {
			System.out.println("OK");
		} System.out.println("OK") System.out.println System.out System System.out "OK" {
			System.out.println("NG");
		} System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args 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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}

} 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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}

} Main
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 max = (B / K) * K;

		if (max >= A){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}

}