using Yorukatsu029.Questions;
using Yorukatsu029.Extensions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace Yorukatsu029.Questions
{
    /// <summary>
    /// ABC129 D
    /// </summary>
    public class QuestionD : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var hw = inputStream.ReadIntArray();
            var h = hw[0];
            var w = hw[1];

            var s = new char[h + 2][];
            s[0] = Enumerable.Repeat('#', w + 2).ToArray();
            s[h + 1] = Enumerable.Repeat('#', w + 2).ToArray();

            for (int i = 1; i <= h; i++)
            {
                s[i] = ("#" + inputStream.ReadLine() + "#").ToCharArray();
            }

            var light = new int[h + 2, w + 2];
            for (int row = 0; row < s.Length; row++)
            {
                var lastWall = 0;
                var streak = 0;
                for (int column = 0; column < s[row].Length; column++)
                {
                    if (s[row][column] == '.')
                    {
                        streak++;
                    }
                    else
                    {
                        for (int repeat = lastWall + 1; repeat < column; repeat++)
                        {
                            light[row, repeat] = streak;
                        }
                        lastWall = column;
                        streak = 0;
                    }
                }
            }

            for (int column = 0; column < w + 2; column++)
            {
                var lastWall = 0;
                var streak = 0;
                for (int row = 0; row < s.Length; row++)
                {
                    if (s[row][column] == '.')
                    {
                        streak++;
                    }
                    else
                    {
                        for (int repeat = lastWall + 1; repeat < row; repeat++)
                        {
                            light[repeat, column] += streak - 1;
                        }
                        lastWall = row;
                        streak = 0;
                    }
                }
            }

            var max = 0;
            for (int row = 0; row < s.Length; row++)
            {
                for (int column = 0; column < s[row].Length; column++)
                {
                    max = Math.Max(max, light[row, column]);
                }
            }

            yield return max;
        }
    }
}


namespace Yorukatsu029
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionD();    // 問題に合わせて書き換え
            var answers = question.Solve(Console.In);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
        }
    }
}

#region Base Classes

namespace Yorukatsu029.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);
    }

}

#endregion

#region Extensions

namespace Yorukatsu029.Extensions
{
    internal static class TextReaderExtensions
    {
        internal static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        internal static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        internal static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        internal static string ReadString(this TextReader reader) => reader.ReadLine();

        internal static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        internal static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        internal static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        internal static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);
    }
}

#endregion

Measured memory_bytes: 44864