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