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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                System.out.println("NG");
            }         
	} main {
    
    Scanner sc = new Scanner(System.in);
        int K = sc.nextInt();
        int A = sc.nextInt();
        int B = sc.nextInt();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                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 if(B/K*K>=A){
                System.out.println("OK");
            }else{
                System.out.println("NG");
            } B/K*K>=A B/K*K B/K B K K A {
                System.out.println("OK");
            } System.out.println("OK") System.out.println System.out System System.out "OK" {
                System.out.println("NG");
            } 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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                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();

            if(B/K*K>=A){
                System.out.println("OK");
            }else{
                System.out.println("NG");
            }         
	}
}
