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