Question: Let's consider the following sequence:

$$9,8,7,6,5,4,3,2,1,0,89,88,87,86,85,84,83,82,81,80,79,78,77,76,75,74,73,72,71...$$
This is the sequence of \$9\$'s complement of a number: that is, \$ a(x) = 10^d - 1 - x \$ where \$ d \$ is the number of digits in \$ x \$. ([A061601](https://oeis.org/A061601) in the OEIS).Your task is to add the first \$n\$ elements.

### Input

A number \$n∈[0,10000]\$.

### Output

The sum of the first \$n\$ elements of the sequence.

### Test cases

```
0 -> 0
1 -> 9
10 -> 45
100 -> 4050
1000 -> 408600
10000 -> 40904100

```

Standard [code-golf](/questions/tagged/code-golf "show questions tagged 'code-golf'") rules apply. The shortest code in bytes wins.

Answer: 
[Zsh](https://www.zsh.org/), 35 bytes
=====================================

```
for ((x=$1;x--;s+=1e$#x+~x)):
<<<$s
```

[Attempt This Online!](https://ato.pxeger.com/run?1=m724qjhjwYKlpSVpuhY3ldPyixQ0NCpsVQytK3R1rYu1bQ1TVZQrtOsqNDWtuGxsbFSKIUqhOpZGGxoYxEI5AA)
[J](http://jsoftware.com/), 24 bytes
====================================

```
+/@((10&^@#@":->:)"0@i.)

```

[Try it online!](https://tio.run/##y/qvpKeepmBrpaCuoKNgoGAFxLp6Cs5BPm7/tfUdNDQMDdTiHJQdlKx07aw0lQwcMvU0/2tycaUmZ@QrpCkYwBiGcAZCyACZicI24PoPAA "J – Try It Online")