Quantifiers

Question

Translate into the predicate logic

One has to drink water in order to survive

D(x) = x drinks water

S(x) = x survives

Comments

$D(x)$ $\Rightarrow$ $S(x)$

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The answer should be: there exists no one who didn't drink water and survived.

$\neg \exists (\neg D(x) \land S(x))$

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@goxul you are right but can you please tell how to determine it i.e when to use S(x) -> D(x) or D(x) -> S(x). As this also being translated as D(x) -> S(x) so it creating confusion