e-olymp
Problems

The root of a cubic equation

The root of a cubic equation

Given a cubic equation

ax3 + bx2 + cx + d = 0 (a0).

It is known that this equation has exactly one root. Find it.

Input

Four integers: a, b, c, d (-1000a, b, c, d1000).

Output

Print one root of the equation with an accuracy of not less than 6 digits after the decimal point.

Time limit 1 second
Memory limit 128 MiB
Input example #1
1 -3 3 -1
Output example #1
1.0000003749
Input example #2
-1 -6 -12 -7
Output example #2
-1.0000000111