#include <iostream>
using namespace std;

int main() {

	int H, W;

	cin >> H >> W;

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

	return 0;
}
