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

public class Main {
	public static void main(String args[]) throws IOException{
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder builder = new StringBuilder();
		while(true){
			String data[] = reader.readLine().split(" ");
			int a= Integer.parseInt(data[0]);
			int b= Integer.parseInt(data[1]);
			
			if(a==0 && b==0)
				break;
			
			for(int y=0,i=0; y<a; y++){
				for(int x=0; x<b; x++){
					builder.append( i++ %2 == 0 ? "#" : ".");
				}
				builder.append("\n");
				if(b%2==0)i++;
			}
			builder.append("\n");
		
		}
		System.out.print(builder);
	}
}
/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