import java.util.*;

class Main{
	public static void main(String[] args){
		Scanner sr = new Scanner(System.in);
		while(true){
			int h = sr.nextInt();
			int w = sr.nextInt();
			if(h==0&&w==0) break;
			for(int y=0; y<h; y++){
				for(int x=0; x<w; x++){
					if((x+y)%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