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