import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException {
        MyReader reader = new MyReader();
        int k = reader.readInt();
        int[] ab = reader.readInts(" ");
        System.out.println(problem165a(k, ab[0], ab[1]));
    }

    private static String problem165a(int k, int a, int b) {
        for (int i = a; i <= b; i++) {
            if (i % k == 0) return "OK";
        }
        return "NG";
    }

    private static class MyReader {
        private final BufferedReader br;
        private MyReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        private String readString() throws IOException {
            return br.readLine();
        }

        private int readInt() throws IOException {
            return Integer.parseInt(readString());
        }

        private String[] readStrings(String regex) throws IOException {
            return readString().split(regex);
        }

        private int[] readInts(String regex) throws IOException {
            String[] strings = readStrings(regex);
            int[] ints = new int[strings.length];
            for (int i = 0; i < ints.length; i++) {
                ints[i] = Integer.parseInt(strings[i]);
            }
            return ints;
        }
    }
}
/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