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