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