Inconsiderate Neighbors

When I moved into my apartment, my landlord said this was a quiet building.  I soon found out that was not the case.  Every other floor is quiet and clean, but mine has furniture lined throughout the hallways, along with trash.  My neighbors also smoke and laugh outside of my door.  Because of the small size of the building, they are well within their rights to smoke in the building, even though the landlord put up a "no smoking" sign.   Also, my lease says no smoking (in the apartment, which explains why they do it in the hallway). The furniture doesn't block the fire exit, so that is not an issue.  There's nothing in the lease about loitering in the hallway.