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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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 int c = 0; c 0 boolean hit = false; hit false for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      } int i = a; int i = a; i a i<=b i b i++ i++ i {
         if(i%k==0){
            hit = true;
         }
      } {
         if(i%k==0){
            hit = true;
         }
      } if(i%k==0){
            hit = true;
         } i%k==0 i%k i k 0 {
            hit = true;
         } hit = true hit true if(hit){
         System.out.println("OK");
      }else{
         System.out.println("NG");
      } hit {
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         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();
      int c = 0;
      boolean hit = false;
      for(int i = a;i<=b;i++){
         if(i%k==0){
            hit = true;
         }
      }
      if(hit){
         System.out.println("OK");
      }else{
         System.out.println("NG");
      }
   }
}