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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) 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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) 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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) System.out.println("NG");
	} main {

		Scanner scan = new Scanner(System.in);

		int K = scan.nextInt();
		int A = scan.nextInt();
		int B = scan.nextInt();
		int temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) 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 temp = 0; temp 0 boolean flag = false; flag false while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		} temp <= B temp B {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		} temp += K temp K if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			} A <= temp && temp <= B A <= temp A temp temp <= B temp B {
				System.out.println("OK");
				flag = true;
				break;
			} System.out.println("OK") System.out.println System.out System System.out "OK" flag = true flag true break; if (!flag) System.out.println("NG"); !flag flag 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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) 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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) 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 temp = 0;
		boolean flag = false;

		while (temp <= B) {
			temp += K;
			if (A <= temp && temp <= B) {
				System.out.println("OK");
				flag = true;
				break;
			}
		}

		if (!flag) System.out.println("NG");
	}
}