Deal n cards from a 52-card deck without replacement. Return the probability of getting exactly k aces.

This is hypergeometric, not binomial: the draws are not independent, because every card taken changes what is left.

$$P = \frac{\binom{4}{k}\binom{48}{n-k}}{\binom{52}{n}}$$

Input

n = 5
k = 1

Output

0.2994736356080894