# Regular expression or automata for language with odd number of 0's and odd number of 1's

Let $$\Sigma=\{0,1\}$$ and $$L=\{u \in \Sigma^* : u \text{ has odd number of 0's and odd number of 1's}\}$$. How can I build a regular expression or an automaton for this language? I have no idea, and I guess $$L$$ is not regular, but I haven't been able to prove it with the pumping lemma.

If it is not regular, can you give me a hint to prove it?

• Hint, it is regular. – Apass.Jack Jan 19 at 0:53