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 = 1; i <= H; i++){
                for(int j = 1; j <= W; j++){
                    if((i + j) % 2 == 0){
                        System.out.print("#");
                    }else{
                        System.out.print(".");
                    }
                }
                System.out.println();
            }

        }

    }
}
