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