For example, $1 \overline{a b c d}$ is a four-digit natural number. It is known that $\overline{a b c d}-\overline{a b c}-\overline{a b}-a=1995$. Try to determine this four-digit number $\overline{a b c d}$
(1995, Beijing Middle School Advanced Mathematics Competition for Junior High School Students)
Solution: For easier analysis, convert the known horizontal expression into a vertical format, we get
$$
\begin{array}{r}
1000 a+100 b+10 c+d \\
-100 a-10 b-c \\
-10 a-b \\
\text { +) } \begin{array}{r}
-a
\end{array} \\
\hline 1000 \times 1+100 \times 9+10 \times 9+5
\end{array}
$$

By the subtraction rule and borrowing, it is not difficult to see that $a=2$.
From $900+200=1100$, and noting that the tens digit of the difference is 9, we can deduce that $b=2$.
Similarly, $90+20+20=130$, so we can deduce that $c=4$.
Also, $5+2+2+4=13$,
thus $d=3$.
Therefore, $\overline{a b c d}=2243$.