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Metamath Proof Explorer

Theorem nnzi

Description: A positive integer is an integer. (Contributed by Mario Carneiro, 18-Feb-2014)

Ref Expression
Hypothesis nnzi.1 ⊢ 𝑁 ∈ ℕ
Assertion nnzi 𝑁 ∈ ℤ

Proof

Step Hyp Ref Expression
1 nnzi.1 ⊢ 𝑁 ∈ ℕ
2 nnssz ⊢ ℕ ⊆ ℤ
3 2 1 sselii ⊢ 𝑁 ∈ ℤ