  A topological group $G$ is called 2-swelling if for any compact subsets
$A,B\subset G$ and elements $a,b,c\in G$ the inclusions $aA\cup bB\subset A\cup
B$ and $aA\cap bB\subset c(A\cap B)$ are equivalent to the equalities $aA\cup
bB=A\cup B$ and $aA\cap bB=c(A\cap B)$. We prove that an (abelian) topological
group $G$ is 2-swelling if each 3-generated (resp. 2-generated) subgroup of $G$
is discrete. This implies that the additive group $\mathbb Q$ of rationals is
2-swelling and each locally finite topological group is 2-swelling.
