JEE Advanced 2024 Chemistry question on Aldehydes Ketones and Acids

Complete reaction of acetaldehyde with excess formaldehyde, upon heating with conc. NaOH solution, gives $\mathbf{P}$ and $\mathbf{Q}$. Compound $\mathbf{P}$ does not give Tollens' test, whereas $\mathbf{Q}$ on acidification gives positive Tollens' test. Treatment of $\mathbf{P}$ with excess cyclohexanone in the presence of catalytic amount of $p$-toluenesulfonic acid (PTSA) gives product $\mathbf{R}$. Sum of the number of methylene groups (-$\mathrm{CH_2}$-) and oxygen atoms in $\mathbf{R}$ is ______.