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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	$⊢ N \in ℕ$
	Assertion	nnzi	$⊢ N \in ℤ$

Step	Hyp	Ref	Expression
1		nnzi.1	$⊢ N \in ℕ$
2		nnssz	$⊢ ℕ \subseteq ℤ$
3	2 1	sselii	$⊢ N \in ℤ$