Functions

Let [ x ] denote the greatest integer \(\le\) x, where x \(\in\) R. If the domain of the real valued function \(f(x) = \sqrt {{{\left| {[x]} \right| - 2} \over {\left| {[x]} \right| - 3}}}\) is (\(-\) \(\infty\), a) \(]\cup\) [b, c) \(\cup\) [4, \(\infty\)), a < b < c, then the value of a + b + c is :