
import java.util.Scanner;


public class Main {
	public static void main(String[] args)
	{
		Scanner scanner = new Scanner(System.in);
		for(;;)
		{
			int w = scanner.nextInt();
			int h = scanner.nextInt();
			
			if(w==0 && h==0)
			{
				break;
			}
			
			for(int i=0; i<w; i++)
			{
				for(int j=0; j<h; j++)
				{
					if((i%2==0 && j%2==0) || (i%2==1 && j%2==1))
					{
						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