Grouped Rows in Excel - Reversing the process in Power BI

Hi Team,

I've got some data that comes from Excel - on the Excel side the rows are grouped so we end up with something like this in Power Query:

I'm trying to avoid doing anything manual on the Excel side, as this report will be updated weekly (hoping to automate) - I want to replicate the results so that it would instead be:
1
1
1
2
2

2

etc. Is there a way to do a Conditional Index, or something else to get the result? For context, this number is the identifier for the rest of the table, none of the other columns will enable me to work with the data in this way.