Contest1390/1390N.cpp

#include<bits/stdc++.h>

using namespace std;

int main() {
    int h, w, z = 0;
    while (cin >> h >> w) {
        if (h == 0 and w == 0)
            break;
        if (z++)
            cout << endl;
        for (int x = 0; x < h; x++) {
            for (int y = 0; y < w; y++) {
                if ((x + y) % 2 == 0)cout << "#";
                else cout << ".";
            }
            cout << endl;
        }
    }
    return 0;
}