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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  }
} 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  }
} 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  } 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  } 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    } 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    } {
      if(a<=(k*i) && (k*i)<=b){
        System.out.println("OK");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    } if(a<=(k*i) && (k*i)<=b){
        System.out.println("OK");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      } 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");
        break;
      } System.out.println("OK") System.out.println System.out System System.out "OK" break; if(i==1000){
        System.out.println("NG");
        break;
      } i==1000 i 1000 {
        System.out.println("NG");
        break;
      } System.out.println("NG") System.out.println System.out System System.out "NG" break; 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  }
} 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  }
} 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");
        break;
      }else if(i==1000){
        System.out.println("NG");
        break;
      }
    }
  }
}
