import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	}

} import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	}

} Main public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	} main {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	} Scanner scan=new Scanner(System.in); scan new Scanner(System.in) int K=scan.nextInt(); K scan.nextInt() scan.nextInt scan int A=scan.nextInt(); A scan.nextInt() scan.nextInt scan int B=scan.nextInt(); B scan.nextInt() scan.nextInt scan int s=0; s 0 s=(B/K)*K s (B/K)*K (B/K) B K K if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		} A<=s A s {
			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 scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	}

} public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	}

} Main
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int K=scan.nextInt();
		int A=scan.nextInt();
		int B=scan.nextInt();
		int s=0;
		s=(B/K)*K;
		if(A<=s)
		{
			System.out.println("OK");
		}
		else
		{
			System.out.println("NG");
		}
	}

}
