[ubuntu] upgrade 12.04 to 13.04

I have just bought a new laptop. It comes with ubuntu 12.04 installed.

I have finished all updates. I expected update manager then to ask me if I want to update to 13.04 but it wants me to update to 12.10

is there anyway to bypass downloading 12.10 and go directly for 13.04 ??
I dont't have a USB stick or any ubuntu live CDs so I can't download from site.

anyway to update directly from 12.04 to 13.04 ??