#include <iostream>
using namespace std;

int main() {
  int h, w;
  while (cin >> h >> w, h | w) {
    for (int i = 0; i < h; i++) {
      for (int j = 0; j < w; j++) {
        if ((i + j) & 1) cout << ".";
        else cout << "#";
      }
      cout << endl;
    }
    cout << endl;
  }
  return 0;
}
