JEE Main 2021 Mathematics question

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 to x. 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 .