3. (8 points) The teacher has a calculator, and each student comes up in turn to input a natural number. The first student inputs 1, the second student inputs 2, the third student inputs 3. Since the buttons 4 and 8 on the calculator are broken, the next student can only input 5, and the following students input 6, 7, 9, 10, 11, 12, 13, 15, and so on. According to this input method, Xiao Ming is the 100th student. The natural number Xiao Ming inputs is $\qquad$.
【Solution】Solution: According to the problem, we know:
In $1-100$, the removed numbers are those with 4 as the unit digit, which are $4,14,24,34,44,54,64,74,84,94$, a total of 10 numbers, and 8 as the unit digit, a total of 20 numbers.

Numbers with 4 as the tens digit are $40,41,42,43,44,45,46,47,48,49$, and 8 as the tens digit, a total of 20 numbers. However, $44,48,88,84$ are each counted one extra time.

Thus, there are $40-4=36$ numbers that cannot be used, and we need to start counting 36 numbers from 100.
101 - 110 has 8 numbers.
111 - 120 has 8 numbers.
121 - 130 has 8 numbers.
131 - 139 has 7 numbers.
In total, $8+8+8+7=31$ numbers.
$150,151,152,153,155$ has 5 numbers, so the final number is 155.
Therefore, the answer is: 155.