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();
			}
		}
	}

}

