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Metamath Proof Explorer

Theorem 1z

Description: One is an integer. (Contributed by NM, 10-May-2004)

		Ref	Expression
	Assertion	1z	$⊢ 1 \in ℤ$

Step	Hyp	Ref	Expression
1		1nn	$⊢ 1 \in ℕ$
2	1	nnzi	$⊢ 1 \in ℤ$