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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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 boolean H=false; H false while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      } B>=A B A {
         if(B%K==0){
            H=true;
         }
         B--;
      } if(B%K==0){
            H=true;
         } B%K==0 B%K B K 0 {
            H=true;
         } H=true H true B-- B if(H==true){
         System.out.println("OK");
      }else{
         System.out.println("NG");
      } H==true H true {
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         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();
      boolean H=false;
      while(B>=A){
         if(B%K==0){
            H=true;
         }
         B--;
      }
      if(H==true){
         System.out.println("OK");
      }else{
         System.out.println("NG");
      }
   }
}
