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-b%k > a || b-b%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-b%k > a || b-b%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-b%k > a || b-b%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-b%k > a || b-b%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-b%k > a || b-b%k == a){
            System.out.println("OK");
        }
        else{
            System.out.println("NG");
        } b-b%k > a || b-b%k == a b-b%k > a b-b%k b b%k b k a b-b%k == a b-b%k b b%k b 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-b%k > a || b-b%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-b%k > a || b-b%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-b%k > a || b-b%k == a){
            System.out.println("OK");
        }
        else{
            System.out.println("NG");
        }
        
    }
}