Speaking of handling, what should I do?

For example, when 2358 13 is used, should it be followed by 4(= 1+3) or 2 1(=8+ 13)?

I understand it as the first case, write 4. In this case, there is a simple rule: loop once every 10 number.

Specifically,

2358 1347 1 1

2358 1347 1 1

2358 1347 1 1

2358 1347 1 1

And the sum of a set of 10 numbers 2358134711is 35.

Therefore, the sum of the numbers before 100 is 100/ 10 * 35 = 350.