Regex to Match Even Length Strings

Example $\Sigma =\{0,1\}$ Find $R$ such that $\mathcal{L}(R)=\{x\in {\Sigma }^{\ast },|x|\text{ is even}\}$ $R=((0+1)(0+1){)}^{\ast }$ Alternatively, $R=(00+01+10+11{)}^{\ast }$