import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		while (true) {
			int height = sc.nextInt();
			int width = sc.nextInt();

			if(height == 0 && width == 0) {
				break;
			} else {

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

			}

		}
		sc.close();
	}
}