using namespace std;

int main(){
	int H, W, h, w;

	while (1){
		cin >> H >> W;
		if (H == 0 && W == 0) break;
		for (int i = 0; i < H; i++){
			for (int j = 0; j < W; j++){
				if (i%2==j%2){
					cout << "#";
				}	else {
					cout << ".";
				}
			}
			cout << endl;
		}
		cout << endl;

	}

	return 0;
}