z=zipWith main=interact$f.lines f x=unlines[y|n<-[0..24],y<-x,n==x!!0!y] x!y=last$foldl(#)[0..][1:[sum[1|s/=t]|t<-y]|s<-x] x#y=scanl1(%)$z(%)x$z(+)y$4:x x%y=min(1+x)y