import java.util.Scanner;

public class Main{
	public static void main(String[]args) {
		 Scanner sc = new Scanner(System.in);

		 while(true){
		 int H = sc.nextInt();
		 int W = sc.nextInt();
		 if(H==0 && W==0) break;

		 for(int i=0 ; i<H ; i++){
			   for(int j=0 ; j<W ; j++) {
			    if((i+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