Macro to copy the header from column B and to repeat to other rows until the next header appears

Hi Team,

I have a column B which has a Header and below the header there are sub headers and the sub headers has its own descriptions. What I would like to have is, copy the sub header to column A and copy that to below cells until the next sub header appears in column B.

I have attached the sheet which hopefully let you know what I am looking for.

First sheet: How the worksheet looks like before running macro

Second sheet: How I am expecting the worksheet should look like after macro

Thanks,

Karthik