import java.util.Scanner;

public class Chessboard {
    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.printf("#");
                        }else{
                            System.out.printf(".");
                        }
                    }
                    System.out.printf("\n");
                }
                System.out.printf("\n");
            }

        }
    }

}

