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

public class Main {
	public static void main(String[] args)throws IOException{
		InputStreamReader isr = new InputStreamReader(System.in);
        BufferedReader br = new BufferedReader(isr);
        
        while (true)
        {
        	String[] list = br.readLine().split(" ");
        	int x = Integer.parseInt(list[1]);
            int y = Integer.parseInt(list[0]);
            if (x == 0 && y == 0)
            	break;
            for (int i = 0; i < y; i++)
            {
            	for (int j = 0; j < x; j++)
            	{
            		if ((i + j) % 2 == 0)
            			System.out.print("#");
            		else
            			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