import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
 
 		while(true){
 			int w = sc.nextInt();
 			int h = sc.nextInt(); 			

 			if(h == 0 && w == 0){break;}

 			for(int i = 1; i <= w; i++){
 				for(int j = 1; j <= h; j++){
 					if((i + j) % 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