import java.util.Scanner;

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 dif = b - a;
		dif += 1;
		for(int i = 0; i < dif; i++) {
			if(a % k == 0) {
				System.out.println("OK");
				return;
			}
			a++;
		}
		System.out.println("NG");

	}

}
/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