Running Total that resets counting when value changes

[Calva]

Hello! I need to run totals of a collumn, but it needs to reset when the value change. It can't run total for group. My data is like this:

Source	Need
1	1
1	2
0	1
0	2
1	1
1	2
1	3
1	4
0	1

The Source collumn always come with 0 or 1. The Need Collumn is what I need. 

[Greg_Deckler · Accepted solution]

@Calva So, this is Cthulhu:

Cthulhu - Microsoft Power BI Community

Also, there is a more complex example, Bride of Cthulhu:

Bride of Cthulhu! - Microsoft Power BI Community