using System;
using System.Collections.Generic;
using System.Linq;

public class Hello
{
    private const int MOD_N = 1000000000 + 7;

    public static void Main()
    {
        var list = Console.ReadLine().Split(' ');
        var h = int.Parse(list[0]);
        var w = int.Parse(list[1]);

        var ss = new bool[h, w];
        for (int i = 0; i < h; ++i)
        {
            var s = Console.ReadLine();
            for (int j = 0; j < s.Length; ++j)
                ss[i, j] = s[j] == '#';
        }

        #if false
        for (int i = 0; i < h; ++i)
        {
            for (int j = 0; j < w; ++j)
                Console.Write(ss[i,j] ? "x" : "o");
            Console.WriteLine();
        }
        #endif

        var hr = new int[h, w];
        var vr = new int[h, w];

        for (int i = 0; i < h; ++i)
        {
            for (int j = 0; j < w; ++j)
            {
                if (ss[i, j])
                {
                    hr[i, j] = vr[i, j] = 0;
                    for (int t = j - 2; t >= 0; --t)
                    {
                        if (hr[i, t] == 0 || hr[i, t + 1] == 0)
                            break;
                        hr[i, t] = hr[i, t + 1];
                    }
                    for (int t = i - 2; t >= 0; --t)
                    {
                        if (vr[t, j] == 0 || vr[t + 1, j] == 0)
                            break;
                        vr[t, j] = vr[t + 1, j];
                    }
                }
                else
                {
                    hr[i, j] = j > 0 ? hr[i, j - 1] + 1 : 1;
                    vr[i, j] = i > 0 ? vr[i - 1, j] + 1 : 1;

                    if (j == w - 1)
                    {
                    for (int t = j - 1; t >= 0; --t)
                    {
                        if (hr[i, t] == 0 || hr[i, t + 1] == 0)
                            break;
                        hr[i, t] = hr[i, t + 1];
                    }
                    }
                    if (i == h - 1)
                    {
                    for (int t = i - 1; t >= 0; --t)
                    {
                        if (vr[t, j] == 0 || vr[t + 1, j] == 0)
                            break;
                        vr[t, j] = vr[t + 1, j];
                    }
                    }
                }
            }
        }

        #if false
        Console.WriteLine("hr");
        for (int i = 0; i < h; ++i)
        {
            for (int j = 0; j < w; ++j)
                Console.Write($"{hr[i,j]} ");
            Console.WriteLine();
        }
        Console.WriteLine("vr");
        for (int i = 0; i < h; ++i)
        {
            for (int j = 0; j < w; ++j)
                Console.Write($"{vr[i,j]} ");
            Console.WriteLine();
        }
        #endif

        int max = 0;

        for (int i = 0; i < h; ++i)
        {
            for (int j = 0; j < w; ++j)
            {
                var t = hr[i, j] + vr[i, j];
                if (t > max)
                    max = t;
            }
        }

        Console.WriteLine(max - 1
                         );
    }

    private static int Comb(int m, int n)
    {
        var t = m - n;
        if (n > t)
            n = t;

        long numerator = 1;
        for (int i = 0; i < n; ++i)
        {
            numerator *= m - i;
            numerator %= MOD_N;
        }
        long denominator = 1;
        for (; n != 0; --n)
        {
            denominator *= n;
            denominator %= MOD_N;
        }

        var inv_denominator = ModInv((int)denominator, MOD_N);
        var ret = (int)(numerator * inv_denominator % MOD_N);

        return ret >= 0 ? ret : ret + MOD_N;
    }

    private static int ModInv(int a, int m)
    {
        int b = m, x = 1, y = 0;
        while (b != 0)
        {
            var t = a / b;
            a -= t * b;
            Swap(ref a, ref b);
            x -= t * y;
            Swap(ref x, ref y);
        }
        x %= m;
        return x >= 0 ? x : x + m;
    }

    private static void Swap<T>(ref T a, ref T b)
    {
        var t = a;
        a = b;
        b = t;
    }
}


Measured memory_bytes: 50120