#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w, i, j;
  for (;;) {
    cin >> h >> w;
    if (h == 0) exit(0);
    for (i = 0; i < h; i++) {
      for (j = 0; j < w; j++) {
        cout << i * j % 2 ? "#" : ".";
      }
      cout << endl;
    }
    cout << endl;
  }
  return 0;
}
