import Data.List
import Text.Printf

g::Double->Double->String->[(Double,Double)]
g _ _ ""=[]
g h w ('0':xs)= g h (w+1) xs
g h w (_:xs) =(h,w):(g h (w+1) xs)

f::Double->[String]->[(Double,Double)]
f _ []=[]
f h (x:xs)=(g h 1 x) ++ (f (h+1) xs)

f2::Double->Double->(Double,Double)->Double
f2 h w (y,x)=sqrt((y-h)*(y-h)+(x-w)*(x-w))

main = do
       e<-getLine
       es<-getContents
       let ts=lines es
           ds=f 1 ts
           (h:w:[])=map read (words e)::[Int]
           anss=[sum(map (f2 (fromIntegral y::Double) (fromIntegral(x)::Double)) ds)|y<-[0..(h+1)],x<-[0..(w+1)],y==0||y==h+1||x==0||x==w+1]
       printf "%.8f" $ minimum anss