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

class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String strNum = "";
		ArrayList<String> squea = new ArrayList<String>();
		while (true) {
			strNum = br.readLine();
			if ("0 0".equals(strNum)) {
				break;
			}
			for (int i = 0; i < Integer.parseInt(strNum.split(" ")[0]); i++) {
				String line = "";
				if ((i % 2) == 0) {
					for (int j = 0; j < Integer.parseInt(strNum.split(" ")[1]); j++) {
						if ((j % 2) == 0) {
							line += "#";
						} else {
							line += ".";
						}
					}
				} else {
					for (int j = 0; j < Integer.parseInt(strNum.split(" ")[1]); j++) {
						if ((j % 2) == 0) {
							line += ".";
						} else {
							line += "#";
						}
					}
				}
				squea.add(line);
			}
			squea.add("");
		}
		for (int i = 0; i < squea.size(); i++) {
			System.out.println(squea.get(i));
		}
	}

}
/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