eolymp
Problems

Equation - 1

Equation - 1

For given positive integer k solve the equation

prb8673.gif

It is known that equation has one root.

Input

One positive integer k (k109).

Output

Print the single root of the equation with 4 decimal digits.

Time limit 1 second
Memory limit 128 MiB
Input example #1
2
Output example #1
1.5723