Counting Values Until Number Reached, Then Returning Cells Counted

[ExtraLarge]

Hello,

I have been unable to locate, or maybe understand, how to construct a function such as this. I have a total list of quantities for items in column "A," and columns from "C" to "S" that count out projected items per day on a day-by-day basis. I would like Excel to start counting from left to right and see how many days it will take to reach the "Ordered Quantity" "A" by adding up the values inside those items-per-day columns. Returning the number of cells it needed to count to get that total value would be fine. Please see the attached document/screenshot for clarification; note that I have already filled in the "Days Worth" column partially manually to demonstrate what I am looking for, and also note that some of the values are rounded, which is why they might seem off (for example row 1 seems like it should be 9 days because of partial quantities). Thank you in advance!

-ExtraLarge

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