SURVIVAL AND PREPPING:
Don't get too hot. Don't get too cold. Don't get injured.
3 Minutes without air.
3 Hours without shelter.
3 Days without water.
3 Weeks without food.
Bullets/firearms, Energy, Food, Medicine/Medical Supplies and Water.
If you're getting started with prepping then get enough supplies to help you survive a day. Then three days. Then a week. Then two weeks. Then a month. Then three months. Then six months. etc...
A requirement to survive. You will die if you don't have one.