What's the minimum amount of calories per day a human being needs in order to just stay alive and maybe also doing the most basics things?

by "the most basic things" I mean for example:

- being able to get up without too much struggle
- being able to walk a certain distance
- being able to lift something not heavy ( let's say around 10 pounds at the most )
Update: I was talking specially when you are in a survival situation
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