How to download kde or gnome from synaptic for offline installation

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http://askubuntu.com – I know how to install GNOME 3 and KDE using apt-get. But i want to know how to, only download, from synaptic package manager, these shells. When i search for kubuntu-desktop in synaptic then the download file shows nearly 4MB but i clearly remember the actual size was near >100 mb. Just for information both are already installed in my laptop. So the question is - How to download the actuall >100 mb KUbuNTU-DESKTOP so that i can just, without any hesitation install it in offline computer which is using ubuntu 12.04. Same for the GNOME 3. Please help me out ! (HowTos)