P17385 [PacNW 2025] Honkai Stress Relief

After finishing her last exam, Audrey decides to relax by playing *Honkai: Star Rail*. On each of the next $n$ days, she plays during an open time interval $(s,e)$. Her smartwatch checks her stress once per day. It independently chooses a real time $t_0$ uniformly at random from the open interval $(a,b)$. If $s

The first line contains three integers $n$, $a$, and $b$ ($1\le n\le20$, $1\le a

Output the probability that Audrey is reported as stressed on at least one day. An answer is accepted if its absolute or relative error is at most $10^{-6}$.