import java.util.Scanner;

class Main {

	public static void main(String[] args) {

		int h, w;

		Scanner stdIn = new Scanner(System.in);

		while (true) {
			h = stdIn.nextInt();
			w = stdIn.nextInt();

			if ((h + w) == 0) {
				System.exit(0);
			}

			for (int i = 0; i < h; i++) {
				if ((i % 2) == 0) {
					for (int j = 0; j < w; j++) {
						if ((j % 2) == 0) {
							System.out.print('#');
						} else {
							System.out.print('.');
						}
					}
				} else {
					for (int j = 0; j < w; j++) {
						if ((j % 2) == 1) {
							System.out.print('#');
						} else {
							System.out.print('.');
						}
					}
				}
				System.out.println();
			}

		}

	}

}