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# Problem D

A Real Challenge

Cow image from
Pixabay

## Input

The input consists of a single integer $a$ ($1 \le a \le 10^{18}$), the area in square meters of Old MacDonaldâ€™s pasture.

## Output

Output the total length of fence needed for the pasture, in meters. The length should be accurate to an absolute or relative error of at most $10^{-6}$.

Sample Input 1 | Sample Output 1 |
---|---|

16 |
16 |

Sample Input 2 | Sample Output 2 |
---|---|

5 |
8.94427190999915878564 |