import java.io.*;
import java.util.*;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		while (true) {
			String[] str = br.readLine().split(" ");
			int h = Integer.parseInt(str[0]);
			int w = Integer.parseInt(str[1]);
			if (h == 0 & w == 0) {
				break;
			}
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {
					if (i % 2 == 0 & j % 2 == 0) {
						System.out.print("#");
					} else if (i % 2 == 0 & j % 2 != 0) {
						System.out.print(".");
					} else if (i % 2 != 0 & j % 2 == 0) {
						System.out.print(".");
					} else if (i % 2 != 0 & j % 2 != 0) {
						System.out.print("#");
					}
				}
				System.out.println("");
			}
			System.out.println("");
		}
	}
}
/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