COUNT involving several columns

Hi, I need to find a formula on cell A2 on the attached file. The formula should show me the count of Customers who buy SKU 1 only.

I tried to use filters across SKU (2-16) where there is "0" and then count all customers who have values >0 on Column B. But this takes a long time and I have to do similar tables quite a few times. I was just hoping if anyone can come up with a more efficient solution to it.

Regards.