Consider a function
\[
y = f(x) \text{ which satisfies the following equation:}
\]
\[
\frac{d^2y}{dx^2} - \frac{dy}{dx} = 0.
\]
As \( x \to -\infty, y = 1 \), and at \( x = 0, y = 2 \). The value of
\[
\frac{dy}{dx} \text{ at } x = 0 \text{ is } _______ \text{ (answer in integer).}