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