#include <iostream>
using namespace std;

int main() {
	int h, w;
	while (true) {
		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 + j) % 2 == 0) cout << "#";
				else cout << ".";
			}
			cout << endl;
		}
		cout << endl;
	}
	return 0;
}
