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(" ");
		 }
		 }
	}
}
