import java.util.Scanner;

class Main {
	public static void main(String[] args) {
		int H, W, i, j;
		Scanner sc = new Scanner(System.in);
		while (true) {
			H = sc.nextInt();
			W = sc.nextInt();
			if (H == 0 && W == 0) break;
			for (i = 0; i < H; i++) {
				for(j = 0; j < W; j++) {
					if ((i + j) % 2 == 0) System.out.print("#");
					else System.out.print(".");
				}
				System.out.println();
			}
			System.out.println();
		}
	}
}

