import java.util.Scanner;

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