In a flight of stairs, if even one step is off 1/8 of an inch or 3mm, it can cause someone to trip.

I like running up stairs. Specially when there are a lot of them.

When I enter a new building, I go slowly, getting a feel of each rise. If it turns out to be not runnable, I then walk the same way all the time. Otherwise, I get to have fun, starting the next time.

That 1 off-step would make me hate whomever worked on that stair. That would increase by the amount of time I would have planned on staying at that place.