Problems
The root of a cubic equation
The root of a cubic equation
Given a cubic equation
a x^3 + b x^2 + c x + d = 0 (a \ne 0)
It is known that this equation has exactly one root. Find it.
Input data
Four integers: a, b, c, d~(-1000 \le a, b, c, d \le 1000).
Output data
Print the root of equation with no less than **6** decimal digits.
Examples
Input example #1
1 -3 3 -1
Output example #1
1.0000003749
Input example #2
-1 -6 -12 -7
Output example #2
-1.0000000111