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();

		String ans = "NG";

		for (int i = 1; i <= 1000; i++) {

			int n = K * i;

			if (A <= n && n <= B) {
				ans = "OK";
				break;
			}
		}

		// 出力
		System.out.println(ans);
	}
}
/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