//Print a Chessboard

#include <iostream>
#include <cassert>

int main()
{
  while (1) {
    int height, width;
    std::cin >> height >> width;

    assert(height >= 0 && height <= 300);
    assert(width >= 0 && width <= 300);
    if (!height && !width) break;

    char color[2] = "#.";
    int  flag = 0;

    for (int h = 0; h < height; ++h) {
      flag = h % 2;
      for (int w = 0; w < width; ++w) {
        std::cout << color[flag];
        flag ^= 1;
      }
      std::cout << std::endl;
    }
    std::cout << std::endl;
  }

  return 0;
}