Question 10
On a circumference, $n\gt 3$ points are chosen and numbered from 1 to $n$ in any order. We will say that two non-consecutive points $a$ and $b$ are related if in one of the two end arcs $a$ and $b$, all points are Marked with numbers less than the marks of $a$ and $b$. Prove that the number of pairs of related points is exactly $n-3$.