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();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			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 sc = new Scanner(System.in);
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	}

} 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();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	} main {
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	} 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 int ans = 0; ans 0 for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		} int i = 1; int i = 1; i 1 i <= (1000 / k) i (1000 / k) 1000 k i++ i++ i {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		} {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		} if (a <= i * k && b >= k * i) {
				ans++;
				break;
			} a <= i * k && b >= k * i a <= i * k a i * k i k b >= k * i b k * i k i {
				ans++;
				break;
			} ans++ ans break; if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		} ans == 1 ans 1 {
			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 sc = new Scanner(System.in);
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	}

} 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();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	}

} 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();
		int ans = 0;
		for (int i = 1; i <= (1000 / k); i++) {
			if (a <= i * k && b >= k * i) {
				ans++;
				break;
			}

		}
		if (ans == 1) {
			System.out.println("OK");
		} else {
			System.out.println("NG");
		}

	}

}