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Problems

The root of a cubic equation

The root of a cubic equation

Time limit 1 second
Memory limit 128 MiB

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