import java.util.Scanner;
public class Main {
	    public static void main(String[] args){
	        Scanner sc=new Scanner(System.in);
	        int i=0,j=0;
	        while(true){
	            int H=sc.nextInt();
	            int W=sc.nextInt();
	            if(H==0&&W==0)break;
	            else for(i=0;i<H;i++){
	                for(j=0;j<W;j++){
	                	if(i%2==1&&j%2==1){
	                    System.out.print("#");
	                	}
	                	else if(i%2==1&&j%2==0)System.out.print(".");
	                	else if(i%2==0&&j%2==1)System.out.print(".");
	                	else System.out.print("#");
	                }
	                System.out.print("\n");
	        }
	            System.out.print("\n");
	    }
	}
	
}

/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