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