#include<iostream>
using namespace std;
int h, w;
int main() {
	while (cin >> h >> w, h) {
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if ((i + j) % 2) cout << ".";
				else cout << "#";
			}
			cout << endl;
		}
		cout << endl;
	}

	return 0;
}

