they're billing -- bigers have lots of wonderful trim. >> usually four story where the rest of the block is three, the define the intersections. >> and because of the larger three or four story buildings, usually two or three over a retail on the ground floor, wha we have i recall force equal mass times acceleration. >> or mass types acceleration equals force. >> was that sir isaac. >> i believe so. >> sir isaac newton. this is the building. the more stories you put on the building, greaterer the mass of the buildings. that's one of the reasons they pose a greater hazard. here's a soft story building we don't know -- >> it could be steel frames in it but we can't see it. that's what you look for where they have glass on two sides. >> a typical problem hopefully retrofitted. i want to point out, Ñithis bui rtion not vul national but they have commercial uses on the ground floor. if these are destroyed, these buildings might collapse a floor, not a huge pile of rubal the likelihood, like in the marina, they come down on the soft story. >> no. what happened in the marina, most buildings got