I stand to be corrected but I'm sure you will get a serious signal loss on a USB cable of that length.
Surely your router has more than one output socket.
Why not get a patch cable and connect the laptop via that.
I have router down satirs and a patch cable running up into the loft and down again into my sons room, must be over 30foot long, no loss of signal at all.
If you go to Belkins web site there is a wizard which will show you all you need.