Zombie streaker

Has it ever happened to you that you appeared in a graveyard with only a shotgun and around you are zombies? No? Well so here it is going to be for the first time. Principle is laughably simple, you have to survive as long as possible and do not worry no help is coming. After few seconds you start to be surrounded by zombies and the only thing you can do is shoot from your weapon. The ammo is hardcore low, of course you can collect it from the ground but still after some time you run out of it. The only thing how to spare some shots is to aim for bigger groups of the green heads.