New house smells like piss need help

So basically my frat moved into this new house and we weren't on the best terms w the frat we took the house from and I think all the brothers from that frat pissed everywhere because the whole house smells like piss. Sooner or later girls are gonna be like why does this place smell like piss and stop coming to our parties I fear so I was wondering how to get rid of a piss smell. Anyone know how we can eliminate this smell? We are thinking of hiring a cleaning crew but I'm curious what other options we have