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;
			} else {
				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(".");
						}
						System.out.println("");
					} else {
						for (int j = 0; j < W; j++) {
							if (j % 2 == 0)
								System.out.print(".");
							else
								System.out.print("#");
						}
						System.out.println("");
					}
				}
			}
		}
		sc.close();
	}

}
