H, W=gets.split.map &:to_i
S=(1..H).map{gets.chomp}
x=(1..H).map{[0]*W}
y=(1..H).map{[0]*W}

i=0
while i<H
    j=c=0
    while j<W
        c=(S[i][j]==?# ? 0 : c+1)
        x[i][j]=c
        j+=1
    end
    j=W-1
    x[i][j]=x[i][j+1] if x[i][j]>0 && x[i][j+1]>0 while 0<=j-=1
    i+=1
end

j=0
while j<W
    i=c=0
    while i<H
        c=(S[i][j]==?# ? 0 : c+1)
        y[i][j]=c
        i+=1
    end
    i=H-1
    y[i][j]=y[i+1][j] if y[i][j]>0 && y[i+1][j]>0 while 0<=i-=1
    j+=1
end

res=0
i=0
while i<H
    j=0
    while j<W
        t=x[i][j]+y[i][j]-1
        res=t if res<t
        j+=1
    end
    i+=1
end
puts res
