# Alloys

Pelle is building a new advanced underground drill. He wants to build the drill out of a new titanium-aluminium-magnesium alloy. Such an alloy can be mixed in many ways. If an alloy is made with the ratios $x, y, z$ ($x + y + z = 1$) of titanium, aluminium and magnesium, the alloy gets a hardness of $xy$, and a price of $x + y$ SEK per kilogram.

Pelle only has a fixed amount of money per kilogram that he can spend on alloys for his drills. What is the maximum hardness he can get on his new alloy?

## Input

The first and only line of input contains a decimal number $c$ ($0 \le c < 2$, between $1$ and $6$ digits after the decimal point) – the amount of money in SEK that Pelle can spend per kilogram alloy.

## Output

Output a single decimal number, the maximum hardness of Pelle’s alloy.

Your answer will be considered correct if you have an absolute error of at most ${10}^{-6}$.

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

1.0 |
0.25 |