I can't understand, why?! I've tried for many times to change accuracy value and borders of searching (is -10000..10000 enough?), can anybody? please, help me?

There is fine mathematical theory about
precision for multyple roots(symbolic algebra of polinomials,Gries,...)
Acording it to achive precision 10^-6 will enouh to
use near 200 digits in all calculations. Thus Java
and BigInteger best way to pass tests.

Did anybody solve this test without long arithmetics?

I found roots of a polynom and then check if they are roots of its derivatives to determine their repeatness, but got WA#14. Is there a better way to calculate roots?