#include<iostream>

using namespace std;

int main() {
	int H, W;

	while (true) {
		cin >> H >> W;

		if (H + W == 0)break;

		for (int i = 0; i < H; i++) {
			for (int j = 0; j < W; j++) {
				cout << (((i + j) % 2 == 0) ? "#" : ".");
			}
			cout << endl;
		}
		cout << endl;
	}

	return 0;
}