import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			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 sc = new Scanner(System.in);
		int n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	} main {
		Scanner sc = new Scanner(System.in);
		int n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = 0; n 0 int a = 0; a 0 int b = 0; b 0 n = sc.nextInt() n sc.nextInt() sc.nextInt sc sc.nextLine() sc.nextLine sc a = sc.nextInt() a sc.nextInt() sc.nextInt sc b = sc.nextInt() b sc.nextInt() sc.nextInt sc int t = b/n; t b/n b n int ans = t*n; ans t*n t n if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		} a <= ans && ans <= b a <= ans a ans ans <= b ans b {
			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 n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			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 n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = 0;
		int a = 0;
		int b = 0;
		n = sc.nextInt();
		sc.nextLine();
		a = sc.nextInt();
		b = sc.nextInt();

		int t = b/n;
		int ans = t*n;

		if(a <= ans && ans <= b){
			System.out.println("OK");
		}else{
			System.out.println("NG");
		}

	}
}