import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv,
    std.functional, std.math, std.numeric, std.range, std.stdio, std.string,
    std.random, std.typecons, std.container;

ulong MAX = 100_100, MOD = 1_000_000_007, INF = 1_000_000_000_000;
alias sread = () => readln.chomp();
alias lread(T = long) = () => readln.chomp.to!(T);
alias aryread(T = long) = () => readln.split.to!(T[]);
alias Pair = Tuple!(long, "x", long, "y", bool, "haspair");
alias PQueue(T, alias less = "a>b") = BinaryHeap!(Array!T, less);

void main()
{
    long h, w;
    scan(h, w);
    auto s = new string[](h);
    foreach (ref e; s)
        e = sread();

    auto cntrow = new long[][](h, w);
    auto cntclm = new long[][](h, w);
    foreach (i; iota(h))
    {
        long p, q;
        while (p < w)
        {
            while (q < w && s[i][q] == '.')
            {
                q++;
            }
            foreach (j; iota(p, q))
            {
                cntrow[i][j] = (q - p);
            }
            q++;
            p = q;
        }
    }
    // cntrow.each!(x => x.writeln());
    foreach (j; iota(w))
    {
        long p, q;
        while (p < h)
        {
            while (q < h && s[q][j] == '.')
            {
                q++;
            }
            foreach (i; iota(p, q))
            {
                cntclm[i][j] = (q - p);
            }
            q++;
            p = q;
        }
    }
    // cntclm.each!(x => x.writeln());
    long ans;
    foreach (i; iota(h))
    {
        foreach (j; iota(w))
        {
            if (s[i][j] == '.')
            {
                ans = max(ans, cntrow[i][j] + cntclm[i][j]);
            }
        }
    }
    writeln(ans - 1);
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}
