Limits, Continuity and Differentiability Part 2

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