Have participants sum up in their answer

I am conducting an experiment on the influence of musical fit on brand recall. After participants watch a slide show and hear music, I ask them to sum up as many brand names as they remember from the slideshow they watched. I need them to type in the answers themselves but don’t want to have to count the number of brands they remember for each of the respondents. Is there an easy way to do this? Having them type in “One, two, three” seems to make it more difficult.