Oh! My math home work

Now, we have a function $f(x) = Ax^2-B \sin x, A \geq 0 , B \geq 0$, here A and B are integer. We want to know minimum x satisfy f(x) = y, and x>=0.

The first line in the input file is an Integer $T(1 \leq T \leq 500)$.
The first line of each test case contains two integer $A, B(0 \leq A, B \leq 10^3)$.
Then a line a integer $y (-10^3 \leq y \leq 10^3)$.

For each test case, output the minimum x. if no such x exists, output “error”.
The answer should accurate to five decimal places.

2
1 0
5
1 1
-2

2.23607
error

BestCoder Round #13