SUMPRODUCT of total qty sold for each SKU

I have a sheet of sales of each item and what qty it sold at a given order over the past month.

I narrowed the sheet down to only 2 columns:
In Column A I have SKU
in Column B I have how many sold

In Column C I would like a total sold for that SKU over the entire 30 days.

I have it sorted by SKU, so there are multiple rows for each SKU as it sold multiple times last month, sometimes at a different qty. Example:
11012 1
11012 4
11012 2
11015 1
11015 1
11019 10
11019 5
11019 8
11019 2
11019 4

Can someone help me with the (SUMPRODUCT I guess) formla for column C, that I can drag down and just get total sold for each SKU in column C

P.S. I had a formula that worked perfect, when I also had item titles in Column B and Qty sold in Column C. Then in Column D I put: =IF(B1<>B2,SUMPRODUCT(--($A$2:$A$10000=A2),($C$2:$C$10000)),"")
But I don't want to use the title anymore and I am sorry to say but I don't know how to change the formula...

thans