#include<bits/stdc++.h>
using namespace std;
int main() {
	while (1) {
		int h, w;
		cin >> h >> w;
		if (h == 0 && w == 0)break;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if ((i + j) % 2 == 0)cout << "#";
				else cout << ".";
			}
			cout << endl;
		}
		cout << endl;
	}
}
	
