Question 4
Determine the largest real number $c$ such that for any $2017$ real numbers $x_{1}, x_{2}, \ldots, x_{2017}$, the inequality
$$
\sum_{i=1}^{2016} x_{i}\left(x_{i}+x_{i+1}\right) \geq c \cdot x_{2017}^{2}
$$
holds.
$$
\sum_{i=1}^{2016} x_{i}\left(x_{i}+x_{i+1}\right) \geq c \cdot x_{2017}^{2}
$$
holds.