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 + j) % 2 == 0){
					System.out.printf("#");
				}else{
					System.out.printf(".");
				}
			}
			System.out.printf("\n");
		}
		System.out.printf("\n");
 		}
	}
}
