using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using static System.Math;
using static System.Array;

namespace AtCoderSolve
{
    class Solve
    {
        const int mod = 1000000007;
        const int INF = 2147483647;
        const long SINF = 9223372036854775807;

        static int H, W;
        static string[] S;
        static long[,] yoko, tate;
        //static int[] a;
       


        public static void Input()
        {
            var cin = new Scanner();
            var input = cin.SplitReader();
            H = input[0];
            W = input[1];
            S = new string[H + 1];
            for(var i = 0; i < H; i++)
            {
                S[i] = Console.ReadLine() + '#';
            }
            var s = new StringBuilder();
            for(var i = 0; i < W + 1; i++)
            {
                s.Append('#');
            }
            S[H] = s.ToString();
            yoko = new long[H, W];
            tate = new long[H, W];

        }

        static void Main(string[] args)
        {
            Input();
            //var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            //Console.SetOut(sw);

            for(var i = 0; i < H; i++)
            {
                int c = 0;
                for (var j = 0; j < W; j++)
                {
                    if (S[i][j] == '#') 
                    {
                        c = 0;
                        continue;
                    }

                    c++;
                    if (S[i][j + 1] == '#')
                    {
                        for (var k = j - c + 1; k <= j; k++) 
                        {
                            yoko[i, k] += c;
                        }
                    }
                }
            }

            for(var i = 0; i < W; i++)
            {
                int c = 0;
                for(var j = 0; j < H; j++)
                {
                    if (S[j][i] == '#')
                    {
                        c = 0;
                        continue;
                    }

                    c++;
                    if (S[j + 1][i] == '#')
                    {
                        for(var k = j - c + 1; k <= j; k++)
                        {
                            tate[k, i] += c;
                        }
                    }
                }
            }


            long ans = 0;
            for(var i = 0; i < H; i++)
            {
                for(var j = 0; j < W; j++)
                {
                    ans = Max(ans, yoko[i, j] + tate[i, j] - 1);
                }
            }


            Console.WriteLine(ans);
            
            //Console.Out.Flush();
        }
    }

    
    

    public class Scanner
    {
        public int[] SplitReader()
        {
            int[] array = Console.ReadLine().Split().Select(int.Parse).ToArray();
            return array;
        }
        public long[] SplitReaderL()
        {
            long[] array = Console.ReadLine().Split().Select(long.Parse).ToArray();
            return array;
        }

        public int[] MultiLineReader(int N)
        {
            int[] ret = new int[N];
            for(var i = 0; i < N; i++)
            {
                ret[i] = int.Parse(Console.ReadLine());
            }

            return ret;
        }
        public long[] MultiLineReaderL(int N)
        {
            long[] ret = new long[N];
            for (var i = 0; i < N; i++)
            {
                ret[i] = long.Parse(Console.ReadLine());
            }

            return ret;
        }

    }
}

    



Measured memory_bytes: 88756