MathNet 2019-part-01 — 184 problems (EN–VI) Question 168

The medians $AA_1$ and $BB_1$ of the triangle $ABC$ intersect at the point $G$. Let $M$ and $N$ be the midpoints of the segments $GA$ and $GB$, and let $K$ and $L$ be the midpoints of the segments $CB_1$ and $CA_1$, respectively. The segments $KN$ and $LM$ intersect at the point $S$.
Find the ratio $CS : SG$.