I pay a share of my Co-op building's mortgage. For 2018, Turbotax wants the outstanding balance at year end - is this my unit's share of balance or the total balance?

I have a mortgage for my unit but also pay for a portion of the building's mortgage through our maintenance fees. The question for mortgage balance at end of 2018 is new. I do not know if I should be looking at the total building's mortgage balance or just my portion based on the number of shares I own in the Co-op. This information is not provided on the 1098 form.