tuxino is right, closing

я тоже так думаю

Did you solve this task?
I have the same problem. I try to solve this kata using C. My programm complestes all 3 sample tests succesfully, but it can't go throw random tests.
I looked numbers in one of them, and it seems like some numbers are not reffered to arifmetical progression.

It doesn't say that you must ensure that the number doesn't go below 0. It is a promise that no test case will result in negative numbers.

But this raises another issue: I'm pretty sure that the random tests (in C# at least) are not constructed in such a way that no negative numbers can occur along the way.

Before posting issues have a look at the top of the page: here 1930 guys passed the C++ kata out of more than 40,000 and the fixed tests are the same in all language. Chances are high that there is a problem in your code.
So it's not a kata issue. Can be a problem in your code and/or maybe you don't identify correctly the failed test. Print the input, your output and a clear sign between each test to see exactly which fails.

Re-read the kata desc carefully. Had to go over it like 3x to nail it.