From English XL Help:

SUMPRODUCT
Multiplies corresponding components in the given arrays, and returns the sum
of those products.
Syntax
SUMPRODUCT(array1,array2,array3, ...)
Array1, array2, array3, ... are 2 to 30 arrays whose components you want to
multiply and then add.

for help on the --, see

http://www.mcgimpsey.com/excel/doubleneg.html

In article , "Uka P."
wrote:

I also don't get the usage of "--". Am I supposed to put it exactly as
you wrote, exchanging only English "countif" to Polish "licz.jezeli"? Or
is it a symbol standing for something different, which I didn't get?