3. For a positive integer $n$, its decimal representation consists only of the digits 0 and 1, and it is divisible by 225. Find the minimum value of $n$.


(Tip: From $25 \mid n$, we know that the last two digits of $n$ are multiples of 25. But since all the digits of $n$ are 0 and 1, the last two digits of $n$ must be 00. From $91n$, we know that the sum of the digits of $n$ is a multiple of 9, so $n$ must contain at least 9 ones. Therefore, the smallest value of $n$ is 11111111100.)