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The most important part of your doomsday stockpile needs to be, WATER. We can survive without food for up to two weeks, of course, that depends on the level of the activity, but without water, humans can survive only a few days. Make sure that you have plenty of water bottles in your storage, and also make sure that it stays safe from some unwanted guests, because you don’t want to suddenly end up without this precious resource once the apocalypse has already started. You could begin stocking up on water now, and be prepared if one day an outbreak occurs, or you could wait till the undead start roaming the streets, but remember that the price of water then will be much higher, and that you might end up paying with your life.