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