|Author:||G. Grenkin||Time limit:||1 sec|
|Input file:||input.txt||Memory limit:||256 Mb|
Once upon a time Marfa Gennadievna bought a pack of 54 playing cards containing two jokers. She put cards face down and chose N cards of them randomly (with uniform probability distribution).
Your program must calculate the probability that there will be at least one joker among chosen cards.
Input file contains a single integer N.
Output file must contain a single real number — required probability with at least 6 correct digits after decimal point.
2 ≤ N ≤ 54
|No.||Input file (
||Output file (|