
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(true) {
            int h = scanner.nextInt();
            int w = scanner.nextInt();

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

            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    System.out.print((i + j) % 2 == 0 ? "#" : ".");
                }
                System.out.print("\n");
            }

            System.out.print("\n");
        }
        scanner.close();
    }
}

