
import java.util.Scanner;

public class Main {
	public static void main(String[] args)
	{
		Scanner stdIn = new Scanner(System.in);
		
		while(true)
		{
			int H = stdIn.nextInt();
			int W = stdIn.nextInt();
			
			if(H==0 && W==0)
			{
				break;
			}
			
			for(int i=0;i<H;i++)
			{
				for(int j=0;j<W;j++)
				{
					if((i+j)%2==0)
					{
						System.out.print('#');
					}
					else
					{
						System.out.print('.');
					}
				}
				System.out.println();
			}
			System.out.println();
		}
	}
}