
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=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		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();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		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();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		sc.close();

	} main {

		Scanner sc = new Scanner(System.in);
		int K = sc.nextInt();
		int A = sc.nextInt();
		int B = sc.nextInt();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		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 int ans=1; ans 1 for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		} int i = 1 ; int i = 1 ; i 1 i <= B i B i++ i++ i {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		} {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		} ans = K * i ans K * i K i if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			} ans >= A && ans <= B ans >= A ans A ans <= B ans B {
				System.out.println("OK");
				break;
			} System.out.println("OK") System.out.println System.out System System.out "OK" break; if(ans > B){
				System.out.println("NG");
				break;
			} ans > B ans B {
				System.out.println("NG");
				break;
			} System.out.println("NG") System.out.println System.out System System.out "NG" break; 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();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		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();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		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();
		int ans=1;

		for(int i = 1 ; i <= B ; i++) {
			ans = K * i;
			if(ans >= A && ans <= B) {
				System.out.println("OK");
				break;
			}else if(ans > B){
				System.out.println("NG");
				break;
			}
		}



		sc.close();

	}

}
