The state space representation of a first-order system is given as
$\overset{\bullet }{x}=-x+u$
$y=x$
where,$x$ is the state variable, $u$ is the control input and $y$ is the controlled output. Let $u=-Kx$ be the control law, where $K$ is the controller gain. To place a closed-loop pole at $-2$, the value of $K$ is ___________________.