An API call succeeds with probability p per attempt, and you will make at most r attempts. Return the probability it succeeds at some point.

$$P = 1 - (1-p)^r$$

A call that fails 20% of the time is down to 0.8% failure after three tries, which is why retries are worth so much more than they look.

Input

p = 0.8
r = 3

Output

0.992