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

public class Main {

	public static void main(String[] args) {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		String str;
		String[] arrStr;
		StringBuilder sb = new StringBuilder();
		try {

			while (true) {
				str = br.readLine();
				arrStr = str.split(" ");

				int h = Integer.parseInt(arrStr[0]);
				int w = Integer.parseInt(arrStr[1]);
				if (h == 0 && w == 0) {
					break;
				}

				boolean iKisu = false;
				for (int i = 0; i < h; i++) {
					iKisu = (i%2==0);
					for (int j = 0; j < w; j++) {
						if ( iKisu ){
							sb.append( j%2==0 ? "#":".");
						}else{
							sb.append( j%2==0 ? ".":"#");
						}
					}
					sb.append("\n");
				}
				System.out.println(sb.toString());
				sb.setLength(0);
			}

		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
/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