Regular Expression

Question

What is the regular expression of

$L = \{ s \in  L$ 

$i$ = no of $1$ in string $s$

$j$ = no of $0$ in string  $s$

$i+j$ is odd  $\}$ ???

Comments

$\left ( 0+1 \right )\left ( 00+01+10+11 \right )^{*}$

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(a(bb)* + b(aa)*)*