import java.io.*;
import java.util.Arrays;
class Main{
	public static void main(String[] args) throws IOException {
		int i,j;
		int[] n = new int[990];
		String[] str = new String[990];
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		for(;;){
			str = in.readLine().split(" ");
			for(i=0;i<2;i++){
				n[i] = Integer.parseInt(str[i]);
			}
			if(n[0]+n[1]==0) break;
			for(i=0;i<n[0];i++){
				for(j=0;j<n[1];j++){
					if(i%2==0 && j%2==0 || i%2!=0 && j%2!=0)
						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