using System;
using System.Collections.Generic;
using System.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        static void Main(string[] args)
        {
            var r = ReadSplit();
            var h = r[0].Int();
            var w = r[1].Int();
            var hw = new string[h][];
            var cDic = new Dictionary<int, int[]>();

            for (int i = 0; i < h; i++)
            {
                var r2 = Read();
                hw[i] = new string[w];
                for (int j = 0; j < w; j++)
                {
                    hw[i][j] = r2[j].ToString();
                }
            }

            for (int i = 0; i < h; i++)
            {
                var l = new int[w];
                var done = new int[w];
                for (int j = 0; j < w; j++)
                {
                    if (hw[i][j] == "#") continue;
                    if (done[j] == 1) continue;
                    var count = 0;
                    while (j + count < w)
                    {
                        if (hw[i][j + count] == "#") break;
                        count++;
                    }
                    for (int k = 0; k < count; k++)
                    {
                        l[j + k] += count;
                        done[j + k] = 1;
                    }
                }
                cDic.Add(i, l);
            }

            for (int i = 0; i < w; i++)
            {
                var l = new int[h];
                var done = new int[h];
                for (int j = 0; j < h; j++)
                {
                    if (done[j] == 1) continue;
                    if (hw[j][i] == "#") continue;
                    var count = 0;
                    while (j + count < h)
                    {
                        if (hw[j + count][i] == "#") break;
                        count++;
                    }
                    for (int k = 0; k < count; k++)
                    {
                        cDic[j + k][i] += count;
                        done[j + k] = 1;
                    }
                }
            }

            var ans = 0;
            for (int i = 0; i < h; i++)
            {
                for (int j = 0; j < w; j++)
                {
                    ans = Math.Max(cDic[i][j] - 1, ans);
                }
            }
            //var hDic = new Dictionary<int, int[]>();
            //var wDic = new Dictionary<int, int[]>();
            //for (int i = 0; i < h; i++)
            //{
            //    var r2 = Read();
            //    var hl = new int[w];
            //    var wl = new int[w];
            //    wDic.Add(i, wl);
            //    var hCount = 0;
            //    for (int j = 0; j < w; j++)
            //    {
            //        if (r2[j] == '.')
            //        {
            //            hCount++;
            //            hl[j] = hCount;
            //            wl[j] = 1;
            //            if (i > 0)
            //            {
            //                wDic[i][j] = wDic[i - 1][j] + 1;
            //            }
            //        }

            //        if(r2[j] == '#' || j == w - 1 || i == h - 1) 
            //        {
            //            var tmp = j - 1;
            //            while (tmp >= 0)
            //            {
            //                if (r2[tmp] == '#') break;
            //                if (tmp < 0) break;
            //                hl[tmp] = hCount;
            //                tmp -= 1;
            //            }
            //            hCount = 0;

            //            var startIndex = i - 1;
            //            if (i == h - 1) startIndex = i;

            //            for (int k = startIndex; k >= 0; k--)
            //            {
            //                if (wDic[k][j] == 0) break;
            //                if (k - 1 < 0) break;
            //                wDic[k - 1][j] = wDic[k][j];
            //            }
            //        }
            //    }
            //    hDic.Add(i, hl);
            //    //wDic.Add(i, wl);
            //}
            //var ans = 0;
            //for (int i = 0; i < h; i++)
            //{
            //    for (int j = 0; j < w; j++)
            //    {
            //        ans = Math.Max(hDic[i][j] + wDic[i][j] - 1, ans);
            //    }
            //}
            WriteRead(ans);
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static string[] ReadSplit()
        {
            return Console.ReadLine().Split(' ');
        }

        public static void WriteRead(object str)
        {
            Console.WriteLine(str);
            Read();
        }

        public static void Write(object str)
        {
            Console.WriteLine(str);
        }

        private static bool ChangeMin<T>(ref T a, T b) where T : IComparable
        {
            if (a.CompareTo(b) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }

        private static bool ChangekMax<T>(ref T a, T b) where T : IComparable
        {
            if (b.CompareTo(a) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }
    }
}


public static class Extentions
{
    public static int Int(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static long Long(this object obj)
    {
        return long.Parse(obj.ToString());
    }

    public static decimal Decimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double Double(this object obj)
    {
        return double.Parse(obj.ToString());
    }

    public static T2 GetValueZero<T1, T2>(this Dictionary<T1, T2> d, T1 key) where T2 : struct
    {
        T2 value;
        if (d.TryGetValue(key, out value))
        {
            return value;
        }
        return new T2();
    }
}



Measured memory_bytes: 197060