#include <iostream>

int main() {
  int h, w;
  while (std::cin >> h >> w, h | w) {
    for (int i = 0; i < h; i++) {
      for (int j = 0; j < w; j++) {
        std::cout << ((i + j) % 2 ? "." : "#");
      }
      std::cout << "\n";
    }
    std::cout << std::endl;
  }
}
