using System;
using System.IO;
using System.Linq;
using System.Net.Configuration;
using System.Runtime.CompilerServices;

namespace Contest
{
    class Program
    {
        private Scanner sc;
        private int H, W;
        private string[] S;
        public void Solve()
        {
            sc = new Scanner();
            H = sc.NextInt();
            W = sc.NextInt();
            S = new string[H];
            for (int i = 0; i < H; i++)
            {
                S[i] = sc.Next();
            }

            int ans = 0;
            var wCnt = new int[H][];
            var hCnt = new int[H][];
            for (int i = 0; i < H; i++)
            {
                hCnt[i] = new int[W];
                wCnt[i] = new int[W];
                int cnt = 0;
                int index = 0;
                for (int j = 0; j < W; j++)
                {
                    if (S[i][j] == '.')
                    {
                        cnt++;
                    }
                    else
                    {
                        for (int k = index; k < j; k++)
                        {
                            wCnt[i][k] = cnt;
                        }
                        cnt = 0;
                        index = j + 1;
                    }
                }

                for (int k = index; k < W; k++)
                {
                    wCnt[i][k] = cnt;
                }
            }
            for (int j = 0; j < W; j++)
            {
                int cnt = 0;
                int index = 0;
                for (int i = 0; i < H; i++)
                {
                    if (S[i][j] == '.')
                    {
                        cnt++;
                    }
                    else
                    {
                        for (int k = index; k < i; k++)
                        {
                            hCnt[k][j] = cnt;
                        }
                        cnt = 0;
                        index = i + 1;
                    }
                }

                for (int k = index; k < H; k++)
                {
                    hCnt[k][j] = cnt;
                }
            }

            //for (int i = 0; i < H; i++)
            //{
            //    Console.WriteLine(string.Join(" ", hCnt[i]));
            //}

            for (int i = 0; i < H; i++)
            {
                for (int j = 0; j < W; j++)
                {

                    ans = Math.Max(ans, hCnt[i][j] + wCnt[i][j] - 1);
                }
            }
            Console.WriteLine(ans);
        }


        static void Main() => new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _stream = new StreamReader(Console.OpenStandardInput());
        _pos = 0;
        _line = new string[0];
        _separator = ' ';
    }
    private char _separator;
    private StreamReader _stream;
    private int _pos;
    private string[] _line;
    #region get a element
    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = _stream.ReadLine().Split(_separator);
            _pos = 0;
        }
        return _line[_pos++];
    }
    public int NextInt()
    {
        return int.Parse(Next());
    }
    public long NextLong()
    {
        return long.Parse(Next());
    }
    public double NextDouble()
    {
        return double.Parse(Next());
    }
    #endregion
    #region convert array
    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }
    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }
    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }
    #endregion
    #region get array
    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = _stream.ReadLine().Split(_separator);
        _pos = _line.Length;
        return _line;
    }
    public int[] IntArray()
    {
        return ToIntArray(Array());
    }
    public long[] LongArray()
    {
        return ToLongArray(Array());
    }
    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }
    #endregion
}

Measured memory_bytes: 57936