1. On a very long road, a race was organized. 20 runners started at different times, each running at a constant speed. The race continued until each runner had overtaken all the slower ones. The speeds of the runners who started first and last were the same, and the speeds of the others were different from theirs and distinct from each other.

What could be the number of overtakes, if each involved exactly two people? In your answer, indicate the largest and smallest possible numbers in any order, separated by a semicolon.

Example of answer format:

$10 ; 20$
Answer: $18 ; 171$ || $171 ; 18$ || 18,171 || 171,18 || $18 ; 171 ;|| 171 ; 18$

Examples of answer notation: $10 ; 20$