The smell of cat urine in the carpet!

So I've just moved into a rental property and the old tennents had cats that obviously peed everywhere and now the house smells of cat urine. When I looked at the place I had a half blocked nose so I couldn't smell it. The owners shampooed the carpet before I moved in and I have since shampooed them again. I've tried vinegar spray, carpet deodorisers both in powder and spray form, extra carpet shampooing, disinfectant, eucalyptus oil spray and I just can't get rid of the smell. I left all the doors and windows open for 2 days before I moved in and all the doors and windows are open when I'm home. There are no stains just a smell and the smell is in all three bedrooms and the longe room. I'm tired of spending money on continual burning candles, incense, air fresheners and other Capet cleaning products. Any ideas on what I can do to get rid of the smell for such a large area?