
#include <iostream>
using namespace std;
int main() {
	int a, b;
	while (true) {
		cin >> a >> b;
		if (a == 0 && b == 0) { break; }
		for (int i = 0; i < a; i++) {
			for (int j = 0; j < b; j++) {
				if ((i + j) % 2 == 0) { cout << '#'; }
				else { cout << '.'; }
			}
			cout << endl;
		}
		cout << endl;
	}
}
