#include <iostream>
#include <string>
#include <stddef.h>
#include <stack>
#include <queue>

using namespace std;

int main() {
	int h, w;
	while (1) {
		cin >> h >> w;
		if (h == 0 && w == 0) break;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if ((h + j) % 2 == 0) cout << '#';
				else cout'.';
			}
			cout << endl;
		}
		cout << endl;
	}
}