  We define $\Delta$-Baire spaces. If a paratopological group $G$ is
$\Delta$-Baire space, then $G$ is a topological group. Locally pseudocompact
spaces, Baire $p$-spaces, Baire $\Sigma$-spaces, products of \v{C}ech-complete
spaces are $\Delta$-Baire spaces.
