import java.util.Scanner;

public class Main {

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

		while(scan.hasNext()) {
			int H = scan.nextInt(), W = scan.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 {
							System.out.print(".");
						}
					}
					System.out.println();
				}
				System.out.println();
			}
		}
		scan.close();
	}

}

