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

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            new ABC129().SolveD(new ConsoleInput(Console.In, ' '));
        }
    }

    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; }
    }
  
  class ABC129
  {
    public void SolveD(ConsoleInput cin)
        {
            var h = cin.ReadInt;
            var w = cin.ReadInt;
            var temp = cin.ReadStrArray(h);
            var S = new List<char[]>();
            for (int i = 0; i < h; i++)
            {
                S.Add(temp[i].ToCharArray());
            }
            //S[y][x] yは下が正の直交座標系
            var Left = new int[w, h];
            var Right = new int[w, h];
            var Up = new int[w, h];
            var Down = new int[w, h];
            for (int y = 0; y < h; y++)
            {
                //WriteLine(S[y]);
                for (int x = 0; x < w; x++)
                {
                    //WriteLine($"x:{x} y:{y}");
                    if (S[y][x] == '#')
                    {
                        Left[x, y] = 0;
                        Up[x, y] = 0;
                    }
                    else
                    {
                        if (x == 0) Left[x, y] = 1;
                        else Left[x, y] = Left[x - 1, y] + 1;
                        if (y == 0) Up[x, y] = 1;
                        else Up[x, y] = Up[x, y - 1] + 1;
                    }
                }
            }
            for (int y = h - 1; y >= 0; y--)
            {
                //WriteLine(S[y]);
                for (int x = w - 1; x >= 0; x--)
                {
                    //WriteLine($"x:{x} y:{y}");
                    if (S[y][x] == '#')
                    {
                        Right[x, y] = 0;
                        Down[x, y] = 0;
                    }
                    else
                    {
                        if (x == w - 1) Right[x, y] = 1;
                        else Right[x, y] = Right[x + 1, y] + 1;
                        if (y == h - 1) Down[x, y] = 1;
                        else Down[x, y] = Down[x, y + 1] + 1;
                    }
                }
            }
            int maxValue = 0;
            for (int y = 0; y < h; y++)
            {
                for (int x = 0; x < w; x++)
                {
                    var sum = Right[x, y] + Up[x, y] + Left[x, y] + Down[x, y] - 3;
                    //WriteLine($"x,y:({x},{y}) r:{Right[x, y]} l:{Left[x, y]} u:{Up[x, y]} d:{Down[x, y]}");
                    if (sum > maxValue) maxValue = sum;
                }
            }

            WriteLine(maxValue);
            ReadLine();
        }
  }
}


Measured memory_bytes: 100304