Since you tagged your question as self-study, I'll not give the full answer here but try to help you get on the right path.
To clarify, you're using $[\bullet]$ to denote the floor function. In which case, since $Y_i$ can take on values 1, 3, and 5, then $\left[ \frac{Y_i}{3} \right]$ can only be 0 or 1 (since 3/3 = 1 and 5/3 = 1.66... which would also get rounded down to 1).
Think about what this means. You can now consider $\left[ \frac{Y_i}{3} \right]$ as your random variable, which can take on 2 values, with probabilities that you can work out from the original probability distribution for $Y_i$.
Note that this essentially reduces the problem to a series of coin tosses with an unfair coin.