Is there a way to count all the field that has been filled by 0?

[Ysaac James Salao]

I'm using a calculated text field to sum all the field value.

Example: 

<!-- @@Formula:

return (issue.get("customfield1") + //(Sample input is 0-5)
issue.get("customfield2") + //(Sample input is 0-5)
issue.get("customfield3") + //(Sample input is 0-5)
issue.get("customfield4") + //(Sample input is 0-5)
issue.get("customfield5") / 5 //(Sample input is 0-5)
-->
Then I will divided it by 5

However, if the customfield1 value is 0, it should be divided by 4.

My idea here is to count all the zero value then I will subtract it 5

Is that possible?