Mac OS Mojave, LO 6.2.5.2

Let’s say I have a spreadsheet containing 4 cells, in each cell is a number, let’s say 1,2,3 & 4 for each respective cell.

How do I calculate the sum of the number of cells with numbers in them (4), rather than the total of the numbers within the cells, to return the result **4**, instead of **10** (as a regular **SUM** formula would produce)?