import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		int k,a,b,x;
		Scanner sc = new Scanner(System.in);
		
		k = Integer.parseInt(sc.next());
		a = Integer.parseInt(sc.next());
		b = Integer.parseInt(sc.next());
		
		sc.close();
		
		x = (b / k) * k;
		if(a <= x) {
			System.out.println("OK");
		}else {
			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