using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace ABC129D
{
    public class Program
    {
        public static void Main(string[] args)
        {
            new Program().Solve(new ConsoleInput(Console.In, ' '));

            return;
        }

        public void Solve(ConsoleInput cin)
        {

            var H = cin.ReadInt;
            var W = cin.ReadInt;
            var map = new char[H, W];
            for (int i = 0; i < H; i++)
            {
                var row = cin.ReadLine.ToCharArray();
                for (int j = 0; j < W; j++)
                {
                    map[i, j] = row[j];
                }
            }

            var left = new int[H, W];
            var right = new int[H, W];
            var up = new int[H, W];
            var down = new int[H, W];

            for (int i = 0; i < H; i++)
            {
                for (int j = 0; j < W; j++)
                {
                    if (map[i, j] == '#')
                    {
                        left[i, j] = 0;
                    }
                    else
                    {
                        if (j == 0)
                        {
                            left[i, j] = 1;
                        }
                        else if (map[i, j - 1] == '#')
                        {
                            left[i, j] = 1;
                        }
                        else
                        {
                            left[i, j] = left[i, j - 1] + 1;
                        }
                    }
                }
            }

            for (int i = 0; i < H; i++)
            {
                for (int j = W - 1; j > -1; j--)
                {
                    if (map[i, j] == '#')
                    {
                        right[i, j] = 0;
                    }
                    else
                    {
                        if (j == W - 1)
                        {
                            right[i, j] = 1;
                        }
                        else if (map[i, j + 1] == '#')
                        {
                            right[i, j] = 1;
                        }
                        else
                        {
                            right[i, j] = right[i, j + 1] + 1;
                        }
                    }
                }
            }

            for (int j = 0; j < W; j++)
            {
                for (int i = 0; i < H; i++)
                {
                    if (map[i, j] == '#')
                    {
                        up[i, j] = 0;
                    }
                    else
                    {
                        if (i == 0)
                        {
                            up[i, j] = 1;
                        }
                        else if (map[i - 1, j] == '#')
                        {
                            up[i, j] = 1;
                        }
                        else
                        {
                            up[i, j] = up[i - 1, j] + 1;
                        }
                    }
                }
            }

            for (int j = 0; j < W; j++)
            {
                for (int i = H - 1; i > -1; i--)
                {
                    if (map[i, j] == '#')
                    {
                        down[i, j] = 0;
                    }
                    else
                    {
                        if (i == H - 1)
                        {
                            down[i, j] = 1;
                        }
                        else if (map[i + 1, j] == '#')
                        {
                            down[i, j] = 1;
                        }
                        else
                        {
                            down[i, j] = down[i + 1, j] + 1;
                        }
                    }
                }
            }

            int ans = 0;
            for (int i = 0; i < H; i ++)
            {
                for (int j = 0; j < W; j++)
                {
                    int tmp = left[i, j] + right[i, j] + up[i, j] + down[i, j] - 3;
                    if (tmp > ans)
                    {
                        ans = tmp;
                    }
                }
            }

            Console.WriteLine(ans);

        }
    }

    public static class Extensions
    {
        public static string Reverse(this string sourse)
        {
            char[] chrAry = sourse.ToCharArray();
            Array.Reverse(chrAry);
            return new string(chrAry);
        }
    }

    public class ConsoleInput
    {
        private readonly System.IO.TextReader _stream;
        private char _separator = ' ';
        private Queue<string> inputStream;
        public ConsoleInput(System.IO.TextReader stream, char separator = ' ')
        {
            this._separator = separator;
            this._stream = stream;
            inputStream = new Queue<string>();
        }
        public string Read
        {
            get
            {
                if (inputStream.Count != 0) return inputStream.Dequeue();
                string[] tmp = _stream.ReadLine().Split(_separator);
                for (int i = 0; i < tmp.Length; ++i)
                    inputStream.Enqueue(tmp[i]);
                return inputStream.Dequeue();
            }
        }
        public string ReadLine { get { return _stream.ReadLine(); } }
        public int ReadInt { get { return int.Parse(Read); } }
        public long ReadLong { get { return long.Parse(Read); } }
        public double ReadDouble { get { return double.Parse(Read); } }
        public string[] ReadStrArray(long N) { var ret = new string[N]; for (long i = 0; i < N; ++i) ret[i] = Read; return ret; }
        public int[] ReadIntArray(long N) { var ret = new int[N]; for (long i = 0; i < N; ++i) ret[i] = ReadInt; return ret; }
        public long[] ReadLongArray(long N) { var ret = new long[N]; for (long i = 0; i < N; ++i) ret[i] = ReadLong; return ret; }
    }
}


Measured memory_bytes: 85568