= Solution
Use the integer normalization $c(\mathbf3)=1$ from <2/b/solution>. For two <fundamental representations>, the specified discrete <gauge anomaly> coefficient is $\mathcal A=q_1+q_2$. Consequently all solutions in the <finite cyclic group> of charges are
$$
\boxed{(q_1,q_2)=(q,-q)\pmod n,\qquad q\in\mathbb Z_n.}
$$
There are $n$ ordered charge pairs. The trivial pair is included: the problem does not require a faithful action. If a faithful action on these <Weyl fermions> were additionally required, one would retain precisely the $q$ coprime to $n$.
This cancels the discrete <gauge anomaly> defined in the paper. Two left-handed <fundamental representations> by themselves have a nonzero pure cubic <SU(3)> <gauge anomaly>; a complete <gauge theory> would need additional <fermions> to cancel it. That separate condition does not alter the requested discrete congruence.
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