import java.util.Scanner;

public class Main {
	public static void main(String[] args) {

		Scanner scnr = new Scanner(System.in);
		int k = scnr.nextInt();
		int a = scnr.nextInt();
		int b = scnr.nextInt();

		int counter = 0;

		for (int i = a; i <= b; i++) {
			if(i % k == 0) {
				counter = counter + 1;
			}
		}

		if (counter == 0) {
			System.out.print("NG");
		}
		else if (counter > 0) {
			System.out.print("OK");
		}
	}
}
/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