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;
            }
            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();
                }
            }
        }
    sc.close();
    }
}
