import java.util.Scanner;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;

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();
		
		int C = (B/K)*K;
		
		if(A <= C) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

} import java.util.Scanner; Scanner java.util import java.util.LinkedList; LinkedList java.util import java.util.PriorityQueue; PriorityQueue java.util import java.util.Queue; Queue 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();
		
		int C = (B/K)*K;
		
		if(A <= C) {
			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 C = (B/K)*K;
		
		if(A <= C) {
			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 C = (B/K)*K;
		
		if(A <= C) {
			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 C = (B/K)*K; C (B/K)*K (B/K) B K K if(A <= C) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		} A <= C A C {
			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 K = sc.nextInt();
		int A = sc.nextInt();
		int B = sc.nextInt();
		
		int C = (B/K)*K;
		
		if(A <= C) {
			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 K = sc.nextInt();
		int A = sc.nextInt();
		int B = sc.nextInt();
		
		int C = (B/K)*K;
		
		if(A <= C) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

} Main
import java.util.Scanner;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;

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();
		
		int C = (B/K)*K;
		
		if(A <= C) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

}