Author:  G. Grenkin  Time limit:  1 sec  
Input file:  input.txt  Memory limit:  256 Mb  
Output file:  output.txt 
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 (input.txt ) 
Output file (output.txt ) 

1 


2 

