3. (48th Slovenian Mathematical Olympiad) Mathieu first wrote down all the numbers from 1 to 10000 in order, then erased those numbers that are neither divisible by 5 nor by 11. Among the remaining numbers, what is the number at the 2004th position?
3. Since 55 is the least common multiple of 5 and 11, in the positive integers not greater than 55, there are exactly $11+5-1=15$ numbers that can be divided by 5 or 11. These numbers are:
$$
\begin{array}{l}
a_{1}=5, a_{2}=10, a_{3}=11, a_{4}=15, a_{5}=20, a_{6}=22, a_{7}=25, a_{8}=30, \\
a_{9}=33, a_{10}=35, a_{11}=40, a_{12}=44, a_{13}=45, a_{14}=50, a_{15}=55 . \\
\text { Also, since } 2004=133 \times 15+9, \text { the number we are looking for is } \\
133 \times 55+a_{9}=133 \times 55+33=7348 .
\end{array}
$$