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

public class Main {
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		for(;;){
			String s=br.readLine();
		    String[] st=s.split(" ");
			int a=Integer.parseInt(st[0]);
			int b=Integer.parseInt(st[1]);
			if(a==0&&b==0)break;
			for(int i=1;i<=a;i++){int m=0;
			
				if(i%2==1){System.out.print("#");m++;}
				for(int l=1;l<=b-m;l++){
					if(l%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