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