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 g = 0;

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