#include <iostream>
using namespace std;

int main()
{
	int h, w;
	char a[] = { '#', '.' };
	while (cin >> h >> w && h != 0) {
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if (i % 2 == 0) cout << a[j % 2];
				else cout << a[!(j % 2)];
			}
			cout << "\n";
		}
		cout << "\n";
	}
}
