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

namespace D_ABC129
{
    class MainClass
    {

        static int[] hw;
        static int[,,] dp;
        static List<string> s;

        public static void Main(string[] args)
        {
            hw = Array.ConvertAll(Console.ReadLine().Split().ToArray(), int.Parse);
            s = new List<string>();
            for (int i = 0; i < hw[0]; i++)
            {
                s.Add(Console.ReadLine());
            }
            dp = new int[hw[0], hw[1], 2];

            var anslst = new List<int>();
            int tmpans = 0;

            for (int i = 0; i < hw[0]; i++)
            {
                for (int j = 0; j < hw[1]; j++)
                {
                    if (s[i][j] != '#')
                    {
                        tmpans = Math.Max(tmpans, Dp(i, j, 0) + Dp(i, j, 1) - 1);
                    }
                }
            }
            Console.WriteLine(tmpans);
        }
        public static int Dp(int i, int j, int k)
        {
            if (dp[i,j,k] != 0)
            {
                return dp[i, j, k];
            }
            else
            {
                if (k == 0)
                {
                    int ans = 0;
                    int ulim = 0;
                    int dlim = hw[0];
                    for (int x = i; x >= 0; x--)
                    {
                        if (s[x][j] != '#')
                        {
                            ans++;
                        }
                        else
                        {
                            ulim = x;
                            break;
                        }
                    }
                    for (int x = i + 1; x < hw[0]; x++)
                    {
                        if (s[x][j] != '#')
                        {
                            ans++;
                        }
                        else
                        {
                            dlim = x;
                            break;
                        }
                    }
                    for (int z = ulim; z < dlim; z++)
                    {
                        dp[z, j, 0] = ans;
                    }
                    return ans;
                }
                else
                {
                    int ans = 0;
                    int llim = 0;
                    int rlim = hw[1];
                    for (int y = j; y >= 0; y--)
                    {
                        if (s[i][y] != '#')
                        {
                            ans++;
                        }
                        else
                        {
                            llim = y;
                            break;
                        }
                    }
                    for (int y = j + 1; y < hw[1]; y++)
                    {
                        if (s[i][y] != '#')
                        {
                            ans++;
                        }
                        else
                        {
                            rlim = y;
                            break;
                        }
                    }
                    for(int z = llim;z<rlim;z++){
                        dp[i,z,1]=ans;
                    }
                    return ans;
                }
            }
        }
    }
}


Measured memory_bytes: 61508