Four point charges lie on the \(x\)-axis: \(+q\) at \(x=-a\), \(+q\) at \(x=+a\), \(-q\) at \(x=-2a\), and \(-q\) at \(x=+2a\) (with \(a>0\)). For \(|x|\gg a\), the electric potential on the \(x\)-axis has leading behavior \(V(x)\sim \dfrac{K}{x^n}\) (where \(K\neq 0\)). What is the value of \(n\)?