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Metamath Proof Explorer

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