var input = ""
process.stdin.resume();
process.stdin.setEncoding('utf-8');
process.stdin.on('data', function(chunk) {
  input += chunk;
});
 
process.stdin.on('end', function() {
  input = input.split("\n");
  i = 0
  while (input[i] != 0) {
    arr = input[i].split(" ");
    if (arr[0] != 0 || arr[1] != 0) {
      for (j = 0; j < arr[0]; j++) {
        h = "";
        for (k = 0; k < arr[1]; k++) {
          if ((j + k) % 2 == 0) {
            h = h + "#";
          } else {
            h = h + ".";
          }
        }
        console.log(h);
      }
      console.log("");
    }
    i++;
  }
});