#include<iostream>
using namespace std;
int main() {
	int h, w;
	cin >> h >> w;
	while (h != 0) {
		int i, j;
		for (i = 0; i < h; i++) {
			for (j = 0; j < w; j++) {
				if ((i+j)%2==0)
					cout << "#";
				else cout << ".";
			}
			cout << endl;
		}
		cout << endl;
		cin >> h >> w;
	}
	return(0);
}
