How to reduce values ​​in EXCEL in the form of a ladder into one line?

Question

excel

There are 28 thousand such values, how can this process be automated?

Answer 1

Too lazy to strain your brains, so here's a simple option:
1) add a new column between the first and second.
2) let's say the value 12886 is in cell A1, then we write in B1 the formula =IF(A1="";"";C2)
(I have LibreOffiice in the screenshot)
3) drag the formula down
4) hide column C (do not delete)
5) repeat for the remaining columns by analogy