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;
			}
			int i, j;
			for (i = 0; i < H; i++) {
				for (j = 0; j < W; j++) {
					if ((i + j) % 2 == 0) {
						System.out.printf("#");
					} else {
						System.out.printf(".");
					}
				}
				System.out.printf("\n");
			}
		}
		sc.close();
	}
}
