import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(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 stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

} Main public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	} main {
		Scanner stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	} Scanner stdIn = new Scanner(System.in); stdIn new Scanner(System.in) int K = stdIn.nextInt(); K stdIn.nextInt() stdIn.nextInt stdIn int A = stdIn.nextInt(); A stdIn.nextInt() stdIn.nextInt stdIn int B = stdIn.nextInt(); B stdIn.nextInt() stdIn.nextInt stdIn int ans = K; ans K for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		} int i = 1; int i = 1; i 1 i++ i++ i {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		} {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		} if(A <= ans) {
				break;
			}else {
				ans += K;
			} A <= ans A ans {
				break;
			} break; {
				ans += K;
			} ans += K ans K if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		} 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 stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

} public class Main {

	public static void main(String[] args) {
		Scanner stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(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 stdIn = new Scanner(System.in);
		int K = stdIn.nextInt();
		int A = stdIn.nextInt();
		int B = stdIn.nextInt();
		
		int ans = K;
		
		for(int i = 1; ; i++) {
			if(A <= ans) {
				break;
			}else {
				ans += K;
			}
		}
		
		if(ans <= B) {
			System.out.println("OK");
		}else {
			System.out.println("NG");
		}
	}

}