// dfmt off
T lread(T=long)(){return readln.chomp.to!T;}T[] lreads(T=long)(long n){return iota(n).map!((_)=>lread!T).array;}
T[] aryread(T=long)(){return readln.split.to!(T[]);}void arywrite(T)(T a){a.map!text.join(' ').writeln;}
void scan(L...)(ref L A){auto l=readln.split;foreach(i,T;L){A[i]=l[i].to!T;}}alias sread=()=>readln.chomp();
void dprint(L...)(lazy L A){debug{auto l=new string[](L.length);static foreach(i,a;A)l[i]=a.text;arywrite(l);}}
static immutable MOD=10^^9+7;alias PQueue(T,alias l="b<a")=BinaryHeap!(Array!T,l);import std, core.bitop;
// dfmt on

void main()
{
    long H, W;
    scan(H, W);
    auto S = new string[](H);
    foreach (i; 0 .. H)
        S[i] = sread();
    auto R = new long[][](H, W);
    auto C = new long[][](H, W);
    foreach (w; 0 .. W)
    {
        long h = 0;
        while (h < H)
        {
            long len = 0;
            while (h + len < H && S[h + len][w] == '.')
                len++;
            foreach (i; h .. h + len)
                C[i][w] = len;
            h += max(1, len);
        }
    }
    foreach (h; 0 .. H)
    {
        long w = 0;
        while (w < W)
        {
            long len = 0;
            while (w + len < W && S[h][w + len] == '.')
                len++;
            R[h][w .. w + len] = len;
            w += max(1, len);
        }
    }
    long ans = 0;
    foreach (h; 0 .. H)
        foreach (w; 0 .. W)
            ans = ans.max(R[h][w] + C[h][w] - 1);
    writeln(ans);
}
