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