import java.util.Scanner;

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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	}

} import java.util.Scanner; Scanner 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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	}

} 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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int k = sc.nextInt(); k sc.nextInt() sc.nextInt sc int a = sc.nextInt(); a sc.nextInt() sc.nextInt sc int b = sc.nextInt(); b sc.nextInt() sc.nextInt sc if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		} a <= b / k * k a b / k * k b / k b k k {
			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" sc.close() sc.close sc String[] args args 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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	}

} 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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	}

} Main
import java.util.Scanner;

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();

		if (a <= b / k * k) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

		sc.close();
	}

}
