import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(sc.hasNext()) {
			int H = sc.nextInt();
			int W = sc.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.printf("#");
					else
						System.out.printf(".");
				System.out.println();
			}
			System.out.println();
		}
	}
}	
