Let \( f : [0,3] \to \mathbb{R} \) be defined by \( f(x) = \min\{x-[x],\, 1+[x]-x\} \) where \( [x] \) is the greater integer less than or equal to \( x \). Let \( P \) denote the set containing all \( x \in [0,3] \) where \( f \) is discontinuous, and \( Q \) denote the set containing all \( x \in (0,3) \) where \( f \) is not differentiable. Then the sum of number of elements in \( P \) and \( Q \) is equal to ________.
