102390: [AtCoder]ABC239 A - Horizon

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.

Constraints

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

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 $10^{-6}$.

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

问题描述

假设从地面以上$x$米的位置看到的地平线距离是$\sqrt{x(12800000+x)}$米，那么从地面以上$H$米的位置看到的地平线距离是多少米？

限制条件

• $1 \leq H \leq 10^5$
• $H$是一个整数。

输入

输入从标准输入按以下格式给出：

$H$

输出

打印答案。
当与裁判答案的绝对或相对误差不超过$10^{-6}$时，你的答案将被视为正确。

样例输入1

333

样例输出1

65287.907678222

我们有$\sqrt{333(12800000+333)} = 65287.9076782\ldots$。输出如65287.91也会被接受。

样例输入2

634

样例输出2

90086.635834623

我们有$\sqrt{634(12800000+634)} = 90086.6358346\ldots$。