Restart a Count within a Column

count test.xlsxI tried searching for the answer previously, but wasn't having much luck with my syntax, so apologies in advance if I overlooked an existing answer here.

I have three columns of data: date of observation, level of observation, and a 1 or 0 depending on whether or not the level of observation exceeds a certain threshold. I am struggling to figure out how to do a running count of the number of 1s in the column that resets and restarts whenever a 0 observation occurs. any insights would be greatly appreciated!