import std.stdio, std.string, std.algorithm, std.conv, std.range;

void main() {
  foreach (string line; lines(stdin)) {
    if (line == "0 0\n")
      break;

    auto inputArray = line.chomp.split.map!(to!int);
    auto h = inputArray[0];
    auto w = inputArray[1];

    for (int i = 0; i < h; i++) {
      for (int j = 0; j < w; j++) {
        if ((i + j) % 2 == 0) {
          write("#");
        } else {
          write(".");
        }
      }
      
      writeln;
    }
    
    writeln;
  }
}