import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int multiple = Integer.parseInt(br.readLine());
		String input = br.readLine();
		String[] inputArray = input.split(" ");
		
		int start = Integer.parseInt(inputArray[0]);
		int end = Integer.parseInt(inputArray[1]);
		
		for (int i = start; i <= end; i++) {
			if (i % multiple == 0) {
				System.out.println("OK");
				System.exit(0);
			}
		}
		System.out.println("NG");
		System.exit(0);
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz