Slider and Math operations question

I am using a slider for whole values from 0 - 3 but don't know how to make sure that the choice of '0' (the starting point) is an actual choice and not just the user skipping the question. I 'solved' it by making the slider go from -1 to 3 and forcing a response. Not ideal.

I then want to use Math Operations (or javascript if needed) to calculate simple sums from the answers. However, regardless of what I try, I am unable to extract the numbers 0 - 3 from the user's answers.

This doesn't work:

```D = $e{ (q://QID13/SelectedAnswerRecode/1 + q://QID13/SelectedAnswerRecode/2 + q://QID13/SelectedAnswerRecode/4 + q://QID16/SelectedAnswerRecode/1 + q://QID16/SelectedAnswerRecode/2 + q://QID16/SelectedAnswerRecode/3 + q://QID16/SelectedAnswerRecode/4 + q://QID15/SelectedAnswerRecode/1 + q://QID15/SelectedAnswerRecode/2 + q://QID15/SelectedAnswerRecode/4 + q://QID15/SelectedAnswerRecode/5 + q://QID12/SelectedAnswerRecode/3 + q://QID12/SelectedAnswerRecode/4 + q://QID12/SelectedAnswerRecode/5) * 2 }```

This yields the numbers as strings and creates an output of "1 + 3 + 0 + 1..."

```${q://QID13/ChoiceNumericEntryValue/1} + ${q://QID13/ChoiceNumericEntryValue/3} + ${q://QID13/ChoiceNumericEntryValue/5} + ${q://QID16/ChoiceNumericEntryValue/1} + ${q://QID16/ChoiceNumericEntryValue/3} + ${q://QID16/ChoiceNumericEntryValue/5} + ${q://QID15/ChoiceNumericEntryValue/1} + ${q://QID15/ChoiceNumericEntryValue/2} + ${q://QID15/ChoiceNumericEntryValue/3} + ${q://QID15/ChoiceNumericEntryValue/4} + ${q://QID12/ChoiceNumericEntryValue/1} + ${q://QID12/ChoiceNumericEntryValue/2} + ${q://QID12/ChoiceNumericEntryValue/3} + ${q://QID12/ChoiceNumericEntryValue/6}```

It comes back with invalid calculation and when I use javascript, it comes back as NaN (not a number).

I suspect it has to do with my choice of a starting point of -1 but I don't know.