Answer
Any negative scalar.
Work Step by Step
Let's say we have the vector $\overrightarrow{v} = \begin{bmatrix} 1\\ 1 \end{bmatrix}$.
If we multiply this vector by the scalar $c=-1$, then the resulting vector $c\overrightarrow{v} = \begin{bmatrix} -1\\ -1 \end{bmatrix}$ will be outside the given area.
