This challenge is one of the interesting challenge till now.
So i downloaded the file from the link given on the challenge page.

Then on intializing the intial packets i realized that this capture file is of uploading a file to a website(ww18.speedyshare.com).

In our case the file has been divided in 4 parts while uploading and if we look the packets which followed the multipart/form-data then there is common .

All the packet no. 182,63,15,116 are followed by packets which have xaa,xab,xac,xad respectively.

So now the saved the media data of the following four files packets.

Then concatenated all the files in to a zip file.