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 < W; i++){
            	for(int j = 0; j < H; 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("");
        }
        sc.close();
    }
}
