import java.util.Scanner;

class Main {

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

	}

}

