Depends upon your GPA and ECs...
To guarantee interviews everywhere I would aim for 40+... but not be sad when you realize the probability of it (sadly 3 of my friends, in my grade got 40+s, my school is crazy).
Honestly aim for the best you can. It really depends upon where you want to apply. Top tier then go for 36, except for Wash U you should go for a bit higher.
Second tier something 33-34... etc...