Problem Statement

Assuming that the horizon seen from a place x meters above the ground is $\sqrt{x(12800000+x)}$ meters away,
find how many meters away the horizon seen from a place H meters above the ground is.

Input

Input is given from Standard Input in the following format:
H

Output

Print the answer.
Your answer will be considered correct when the absolute or relative error from the judge's answer is at most 10^{-6}.

Constraints

• $1 \leq H \leq 10^5$
• H is an integer.

Sample Input 1

333

Sample Output 1

65287.907678222

We have $\sqrt{333(12800000+333)} = 65287.9076782\ldots.$ Outputs such as 65287.91 would also be accepted.

Sample Input 2

634

Sample Output 2

90086.635834623

We have $\sqrt{634(12800000+634)} = 90086.6358346\ldots$.

见题面 Input 部分

见题面 Output 部分