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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			System.out.println("NG");
	} main {
		Scanner sc = new Scanner(System.in);
		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			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 sc.close() sc.close sc for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		} int i = 1; int i = 1; i 1 i <= 1000 i 1000 i++ i++ i {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		} {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		} int result = i * k; result i * k i k if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			} a <= result && result <= b a <= result a result result <= b result b {
                System.out.println("OK");
                return;
			} System.out.println("OK") System.out.println System.out System System.out "OK" return; 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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			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();
		sc.close();
		for (int i = 1; i <= 1000; i++) {
            int result = i * k;
            if (a <= result && result <= b) {
                System.out.println("OK");
                return;
			}
		}
			System.out.println("NG");
	}

}
