5. 100 999 in ascending order, forming a multi-digit number:
$$
100101102103104 \cdots 997998999
$$

In this multi-digit number, any two adjacent digits are considered a pair, and there are $\qquad$ pairs where the sum of the two

digits is a multiple of 3. (Note: 0 is not considered a multiple of 3)
\begin{tabular}{c}
5 \\
\hline 897
\end{tabular}