Problems
Functional equation
Functional equation
Let $f: R → R, x \ne 0$.
$$
2f(x) + f(1/x) = x
$$
Given value of $x$. Find the value of $f(x)$.
\InputFile
One real number $x, x \ne 0$.
\OutputFile
Print the value of $f(x)$ with $4$ decimal digits.
Input example #1
1
Output example #1
0.3333