$f(x)=\left\{\begin{array}{cl}\frac{\left(2 x^2-a x+1\right)-\left(a x^2+3 b x+2\right)}{x+1}, & \text { if } x \neq-1 \\ k_k, & \text { if } x=-1\end{array}\right.$

is a real valued function. If $a, b, k \in R$ and $f$ is continuous on $R$, then $k=$

$$\lim _\limits{x \rightarrow-\infty} \log _e(\cosh x)+x=$$