import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

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 N=1;
    boolean judge=false;
    boolean judge1=true;
    while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    }
    if(judge==true){
      System.out.println("OK");
    }else{
      System.out.println("NG");
    }




  }
} import java.util.Scanner; Scanner java.util import java.util.Arrays; Arrays java.util import java.util.ArrayList; ArrayList java.util import java.util.List; List java.util import java.util.stream.Collectors; Collectors java.util.stream 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 N=1;
    boolean judge=false;
    boolean judge1=true;
    while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    }
    if(judge==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();
    int N=1;
    boolean judge=false;
    boolean judge1=true;
    while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    }
    if(judge==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();
    int N=1;
    boolean judge=false;
    boolean judge1=true;
    while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    }
    if(judge==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 int N=1; N 1 boolean judge=false; judge false boolean judge1=true; judge1 true while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    } judge1==true judge1 true {
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    } if(K*N>=A&K*N<=B){
          judge=true;
          break;
      } K*N>=A&K*N<=B K*N>=A K*N K N A K*N<=B K*N K N B {
          judge=true;
          break;
      } judge=true judge true break; if(K*N-B>0){
        judge=false;
        break;
      } K*N-B>0 K*N-B K*N K N B 0 {
        judge=false;
        break;
      } judge=false judge false break; N++ N if(judge==true){
      System.out.println("OK");
    }else{
      System.out.println("NG");
    } judge==true judge 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
import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

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 N=1;
    boolean judge=false;
    boolean judge1=true;
    while(judge1==true){
      if(K*N>=A&K*N<=B){
          judge=true;
          break;
      }
      if(K*N-B>0){
        judge=false;
        break;
      }
       N++;
    }
    if(judge==true){
      System.out.println("OK");
    }else{
      System.out.println("NG");
    }




  }
}
