I had a question and that was required to estimate what is the paint required to Paint a Skyscrapper

What I did was to evaluate the room I am sitting in with my interviewer and said that I believe that this room that is 4m*2m of area 8m2 requires half a bucket.

Now I estimated that specific skyscrapper had 50 floors.

For the length or height of each floor, I estimated that I am 1.8m in height and the height is almost 2x so thats one part of my equation. So the height is 50*1.8*2=180m (Is this analogy right?)

For the width I am confused, I wanted to use d=s*t but the issue is that I don't know how to calculate time. If I were to start at point A in the building, how much time does it take me to circle back to A. How can I know that and I don't even know whether A is the mid point or the starting point.

The building in question is somewhat oval similar to The Gerkin in London and would it matter really is the building is spherical or oval or rectangular like a hotel?

Please do let me know what is the best way to approach it.