38. At a math club meeting, the students were offered the following math trick:

Write down any number,

I'll take a look at it

And then on a piece of paper

I'll put it in an envelope in front of you.

Under your number, any

Write down a number again,

And I will allow myself

To write down one number.

We will draw a line and add up

Our neat row of numbers.

No mistakes? Be more careful?!

Everything in order? I'm very glad!

The sum - I ask, check! -

I have had it in the envelope for a long time!

What's the trick here? What's the secret?

Give me your answer.

Try to uncover the secret of this trick.
38. Let's say, for example, the numbers 58431 and 61388 were recorded. The guesser added such a third addend that, when added to the second number recorded by the children, it would result in a number consisting only of nines. For example, $61388 + 38611 = 99999$. The sum of the three addends can be easily obtained using the number 58431, by placing the digit 1 at the far left, reducing the units digit by 1, and leaving all other digits unchanged. The guesser placed the number 158430 in the envelope.