import java.util.Scanner;

public class Main{

	public static void main(String[] args) {
	    Scanner sc = new Scanner(System.in);
		int x,y,i=0,j=0;
		
		while(true){
			x = sc.nextInt();
			y = sc.nextInt();
			if(x == 0){
				sc.close();
				System.exit(0);
			}
			else{
				for(i=0;i<x;i++){
				    if(i%2 == 0){
				    	for(j=0;j<y;j++){
				    	    if(j%2 == 0){
				    		    System.out.print('#');
				    	    }
				    	    else{
				    	        System.out.print('.');
				    	    }
				    	}
				    }
				    else{
				    	for(j=0;j<y;j++){
				    		if(j%2 == 0){
				    			System.out.print('.');
				    		}
				    		else{
				    			System.out.print('#');
				    		}
				    	}
				    }
				    System.out.println();
				}
			}
			System.out.println();
		}
	}
