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

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            var input = ReadArrayInt();
            var H = input[0];
            var W = input[1];
            var grid = new char[H, W];
            for (int i = 0; i < H; i++)
            {
                var line = Read();
                for (int j = 0; j < W; j++)
                {
                    grid[i, j] = line[j];
                }
            }
            var tate = new int[H, W];
            var yoko = new int[H, W];
            for (int i = 0; i < W; i++)
            {
                var sta = 0;
                var idx = 0;
                var cnt = 0;
                while (idx < H)
                {
                    if (grid[idx, i] == '#')
                    {
                        if (cnt == 0)
                        {
                            tate[idx, i] = -1;
                            sta = idx + 1;
                        }
                        else
                        {
                            for (int j = sta; j < idx; j++)
                            {
                                tate[j, i] = cnt;
                            }
                            sta = idx + 1;
                            cnt = 0;
                        }
                    }
                    else
                    {
                        cnt++;
                    }
                    idx++;
                }
                if (cnt > 0)
                {
                    for (int j = sta; j < H; j++)
                    {
                        tate[j, i] = cnt;
                    }
                }
            }
            for (int i = 0; i < H; i++)
            {
                var sta = 0;
                var idx = 0;
                var cnt = 0;
                while (idx < W)
                {
                    if (grid[i, idx] == '#')
                    {
                        if (cnt == 0)
                        {
                            yoko[i, idx] = -1;
                            sta = idx + 1;
                        }
                        else
                        {
                            for (int j = sta; j < idx; j++)
                            {
                                yoko[i, j] = cnt;
                            }
                            sta = idx + 1;
                            cnt = 0;
                        }
                    }
                    else
                    {
                        cnt++;
                    }
                    idx++;
                }
                if (cnt > 0)
                {
                    for (int j = sta; j < W; j++)
                    {
                        yoko[i, j] = cnt;
                    }
                }
            }
            var ans = 0;
            for (int i = 0; i < H; i++)
            {
                for (int j = 0; j < W; j++)
                {
                    var chk = tate[i, j] + yoko[i, j] - 1;
                    if (chk > ans) ans = chk;
                }
            }

            Console.WriteLine(ans);
            Console.ReadLine();
        }

        static string Read() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Read()); }
        static long ReadLong() { return long.Parse(Read()); }
        static int[] ReadArrayInt() { return Read().Split(' ').Select(s => int.Parse(s)).ToArray(); }
        static long[] ReadArrayLong() { return Read().Split(' ').Select(s => long.Parse(s)).ToArray(); }
    }
}

Measured memory_bytes: 56264