The longitudinal section of a runway provides the following data:

$$\begin{array}{|lc|cI|}\hline

&\textbf{End-to-end runway $\textbf{(m)}$} & \textbf{Gradient $(\%)$} \\ \hline &\text{$0$ to $300$} & \text{$+1.2$} \\ \hline &\text{$300$ to $600$} & \text{$-0.7$}\\ \hline

&\text{$600$ to $1100$} & \text{$+0.6$} \\ \hline

&\text{$1100$ to $1400$} & \text{$-0.8$} \\ \hline

&\text{$1400$ to $1700$} & \text{$-1.0$} \\ \hline \end{array}$$

The effective gradient of the runway (in $\%$, $\textit{round off to two decimal places}$) is ________________