Here $Q=4\pi \epsilon_0 RV$ and $ C=4\pi \epsilon_0 R$

While solving i got the energy loss when S2 is closed as $$E_i-E_f = \frac{Q^2}{2C} - (\frac{Q^2}{8C} + \frac{Q^2}{8C})$$

since $Q$ on 1st capacitor equally divides between 1st and 2nd capacitor.

So energy loss when S2 is closed is $\frac{Q^2}{4C}$ and that when S3 is closed is $\frac{Q^2}{16C}$ and so on.

When I take the sum I get $\frac43\pi\epsilon_0 RV^2$ but that's not the answer.

What went wrong?