import java.io.IOException;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in); // ??\???????????????
		StringBuilder out = new StringBuilder(); // ??¨?????¨??¢??°
		StringBuilder output = new StringBuilder(); // #,\n???????´?????????¢??°

		while (true) { // ???????????????
			int H = sc.nextInt(); // ????????\??????
			int W = sc.nextInt(); // ?¨??????\??????

			if (H + W == 0) // ?????¨?¨????0 0????????????
				break;

			for (int i = 0; i < H; i++) {// ????????°???????????????
				for (int j = 0; j < W; j++) {// ?¨??????°???????????????
					if((i % 2 == 0 && j % 2 == 0) || (i % 2 == 1 && j % 2 == 1)){
						out = out.append("#");
					}else{
						out = out.append(".");
					}
				}
				out = out.append("\n");
			}
			output = output.append(out + "\n"); // ????´???????#,\n???????´?
			out.delete(0, out.length()); // ??¨?????¨out????????????
		}
		System.out.print(output); // ??????
		sc.close();
	}

}
/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