import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class Main{
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder sb = new StringBuilder();
		while(true){
			String[] line = br.readLine().split(" ");
			int h = Integer.parseInt(line[0]);
			int w = Integer.parseInt(line[1]);
			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) || (i % 2 != 0 && j % 2 == 0) ) sb.append(".");
					else sb.append("#");
				}
				sb.append("\n");
			}
			sb.append("\n");
		}
		System.out.print(sb);
	}
}
/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