Theorem 4nn0

Description: 4 is a nonnegative integer. (Contributed by Mario Carneiro, 18-Feb-2014)

	Ref	Expression
Assertion	4nn0	|- 4 e. NN0

Proof

Step	Hyp	Ref	Expression
1		4nn	|- 4 e. NN
2	1	nnnn0i	|- 4 e. NN0