About Countable Support iteration of Proper forcing notions and CH

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Assume $CH$. $P$ is a countable support iteration of proper forcing notions of length $ \lt \omega_2$ and each forcing notion is forced to have size $ \le\omega_1$.

I can’t show $P$ forces $CH$. I tried to count the nice names for subsets of $\omega$,but I think the names are less than $|P|^{\omega\cdot |P|}=2^{\omega_1} $, it’s too large.

Please help me. I would appreciate any advice.