Force integers in constant sum question

I am trying to replicate a gallery walk that was done in-person with a constant sum question in Qualtrics. For the gallery walk there were several categories presented and participants had three sticky dots that they placed on the categories to vote for their favorites.

I have been able to set up the constant sum question so I have one column where respondents will assign a value of 0-3 to the row. And also have validation on it so that the total must equal 3. But in testing I found that someone can enter 1.5 in two rows and still pass. I would like to force them to use only integers so they can't work the system and vote for more than 3 options. Any advice on how I can add this extra validation?

The only allowable answers I want are:
* Assign a value of 3 to one row and 0 to the rest
* Assign a value of 1 to three rows and 0 to the rest
* Assign a value of 1 to a row and 2 to a different row then 0 for the rest

Thanks for the help!