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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		System.out.println("NG");

	} main {
		Scanner sc = new Scanner(System.in);

		int k = sc.nextInt();
		int a = sc.nextInt();
		int b = sc.nextInt();

		int dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		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 dif = b - a; dif b - a b a dif += 1 dif 1 for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		} int i = 0; int i = 0; i 0 i < dif i dif i++ i++ i {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		} {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		} if(a % k == 0) {
				System.out.println("OK");
				return;
			} a % k == 0 a % k a k 0 {
				System.out.println("OK");
				return;
			} System.out.println("OK") System.out.println System.out System System.out "OK" return; a++ a 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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		System.out.println("NG");

	}

}