How to uniquely mark a subtotal as 1 and rest all values as 0 in DAX?

[anish610]

Consider this image as a Power Bi matrix table. 
Here I have parent-child hierarchy as rows and in values measure I want to uniquely mark subtotal "A" as 1 and rest all subtotals and child values as 0.

The reason I want to this achieve is then I can add custom value to the subtotal of A.
Ex- 

How can I implement such a measure in DAX? Kindly help.
I tried to explore HASONEVALUE and ISFILTERED its not working for me.
Thank in advance.

@amitchandak @Greg_Deckler 

[Greg_Deckler]

@anish610 Try:

Measure = IF( ISINSCOPE('Table'[Child]), 0, 1 )

See attached PBIX below signature.