import java.util.InputMismatchException;
import java.util.Scanner;

public class Main{


	public static void main(String[] args){

    	Scanner scan = new Scanner(System.in);

			while(true){
				try{
            int H=scan.nextInt();
			int W=scan.nextInt();
			if(H==0&&W==0)break;

			for(int i=0;i<H;i++){
				for(int j=0;j<W;j++){
					if(i%2==0&&j%2==0){System.out.print('#');}
					else if(i%2==0&&j%2==1){System.out.print('.');}
					else if(i%2==1&&j%2==0){System.out.print('.');}
					else if(i%2==1&&j%2==1){System.out.print('#');}

				}System.out.print('\n');
			  }System.out.print('\n');

				}catch(InputMismatchException e){
					System.out.println("??¨??????:"+e);

				}

			}
        	scan.close();


	}

}
/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