import 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	}
} import java.util.*; util.* java 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	}
} 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	} main {
		Scanner sc = new Scanner(System.in);
		int K = sc.nextInt();
		int A = sc.nextInt();
		int B = sc.nextInt();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	} 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 String s = "NG"; s "NG" for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		} int i = 0; int i = 0; i 0 i <= B - A i B - A B A i ++ i ++ i {
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		} {
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		} int x = A + i; x A + i A i if(x % K == 0){
			s = "OK";
			break;
			} x % K == 0 x % K x K 0 {
			s = "OK";
			break;
			} s = "OK" s "OK" break; System.out.println(s) System.out.println System.out System System.out s 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	}
} 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	}
} Main
import 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();
		String s = "NG";

		for(int i = 0; i <= B - A; i ++){
			int x = A + i;
			if(x % K == 0){
			s = "OK";
			break;
			}
		}

		System.out.println(s);
	}
}