import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(true) {
			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 % 2 == 0 && j % 2 == 0) || (i % 2 == 1 && j % 2 == 1)) {
						System.out.print("#");
					} else {
						System.out.print(".");
					}
				}
				System.out.println();
			}
			System.out.println();
		}
	}
}