import java.util.*;

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 temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        System.out.println("NG");
    }
} import java.util.*; util.* java 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 temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        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 temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        System.out.println("NG");
    } main {
        Scanner sc=new Scanner(System.in);
        int K=sc.nextInt();
        int A=sc.nextInt();
        int B=sc.nextInt();
        int temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        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 temp=K; temp K while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        } B>=temp B temp {
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        } if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            } A<=temp A temp {
                System.out.println("OK");
                System.exit(0);
            } System.out.println("OK") System.out.println System.out System System.out "OK" System.exit(0) System.exit System 0 {
                temp+=K;
            } temp+=K temp K System.out.println("NG") System.out.println System.out System System.out "NG" String[] args args
import java.util.*;

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 temp=K;
        while(B>=temp){
            if(A<=temp){
                System.out.println("OK");
                System.exit(0);
            }else{
                temp+=K;
            }
        }
        System.out.println("NG");
    }
}