import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        int k = Integer.parseInt(br.readLine());
        String[] in = br.readLine().split(" ");
        int a = Integer.parseInt(in[0]);
        int b = Integer.parseInt(in[1]);

        br.close();

        String ans = "NG";

        for (int i = a; i <= b; i++) {
            if (i % k == 0) {
                ans = "OK";
            }
        }

        bw.write(ans);

        bw.flush();

    }
}
/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