Excel argument/formula question

Let’s say I have the POTENTIAL to have data in cellS A1, B1, C1 and D1. In cell E1 I want to add all four cells together. That’s easy. Now in cell F1 I want to say take the total from E1 and divide it by the number of cells that have data. One time all four cells may have data. Another time maybe only two cells have data. Does anyone know a formula that will say, I see data in cells A1, B1 and C1 so divide E1 by 3. And then the next time if all four cells have data it will automatically divide by 4, or is this not a possible argument / formula in Excel.
Many thanks in advance.