using System;
using System.Collections.Generic;
//using System.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        private static long mod = 1000000007;
        private static long max = 999999999999;

        static void Main(string[] args)
        {
            var r = ReadSplit();
            var h = r[0].Int();
            var w = r[1].Int();
            var l = new char[h][];
            
            for (int i = 0; i < h; i++)
            {
                l[i] = new char[w];
                var s = Read();
                for (int j = 0; j < w; j++)
                {
                    l[i][j] = s[j];
                }
            }
            var countCol = new int[h][];
            for (int i = 0; i < h; i++)
			{
                countCol[i] = new int[w];
                var c = 0;
			    for (int j = 0; j < w; j++)
			    {
                    if (l[i][j] == '.')
                    {
                        c++;
                    }
                    else
                    {
                        c = 0;
                    }
                    countCol[i][j] = c;
			    }
			}

            var countRow = new int[h][];
            for (int i = 0; i < h; i++)
            {
                countRow[i] = new int[w];
            }

            for (int j = 0; j < w; j++)
            {
                var c = 0;
                for (int i = 0; i < h; i++)
                {
                    if (l[i][j] == '.')
                    {
                        c++;
                    }
                    else
                    {
                        c = 0;
                    }
                    countRow[i][j] = c;
                }
            }

            for (int i = 0; i < h; i++)
            {
                var pre = 0;
                for (int j = w - 1; j >= 0; j--)
                {
                    if (pre == 0)
                    {
                        pre = countCol[i][j];
                    }
                    if (countCol[i][j] == 0)
                    {
                        pre = 0;
                    }
                    else
                    {
                        countCol[i][j] = pre;
                    }
                }
            }

            for (int j = 0; j < w; j++)
            {
                var pre = 0;
                for (int i = h - 1; i >= 0; i--)
                {
                    if (pre == 0)
                    {
                        pre = countRow[i][j];
                    }
                    if (countRow[i][j] == 0)
                    {
                        pre = 0;
                    }
                    else
                    {
                        countRow[i][j] = pre;
                    }
                }
            }

            var ans = 0;
            for (int i = 0; i < h; i++)
            {
                for (int j = 0; j < w; j++)
                {
                    var a = countCol[i][j];
                    var b = countRow[i][j];
                    var tmp = a + b;
                    if (a > 0 && b > 0)
                    {
                        tmp--;
                    }
                    ans = Math.Max(ans, tmp);
                }
            }

            WriteRead(ans);
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static string[] ReadSplit()
        {
            return Console.ReadLine().Split(' ');
        }

        public static void WriteRead(object str)
        {
            Console.WriteLine(str);
            Read();
        }

        public static void Write(object str)
        {
            Console.WriteLine(str);
        }

        private static bool ChangeMin<T>(ref T a, T b) where T : IComparable
        {
            if (a.CompareTo(b) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }

        private static bool ChangekMax<T>(ref T a, T b) where T : IComparable
        {
            if (b.CompareTo(a) > 0)
            {
                a = b;
                return true;
            }
            return false;
        }

        private static bool NextPermutation(int[] array)
        {
            var size = array.Length;
            var ok = false;

            //array[i]<array[i+1]を満たす最大のiを求める
            int i = size - 2;
            for (; 0 <= i; i--)
            {
                if (array[i] < array[i + 1])
                {
                    ok = true;
                    break;
                }
            }

            //全ての要素が降順の場合、NextPermutationは存在しない
            if (ok == false) return false;

            //array[i]<array[j]を満たす最大のjを求める
            int j = size - 1;
            for (; ; j--)
            {
                if (array[i] < array[j]) break;
            }

            //iとjの要素をswapする
            var tmp = array[i];
            array[i] = array[j];
            array[j] = tmp;

            //i以降の要素を反転させる
            Array.Reverse(array, i + 1, size - (i + 1));

            return true;
        }

        //要素数Nを引数として渡し、0～N-1でできた順列をすべて返す
        static List<int[]> GetAllPermutation(int N)
        {
            var res = new List<int[]>();
            var array = Enumerable.Range(0, N).ToArray();
            do
            {
                var copy = new int[N];
                array.CopyTo(copy, 0);
                res.Add(copy);
            } while (NextPermutation(array));

            return res;
        }

        //配列arrayを引数として渡し,辞書順がarray以上の順列をすべて返す
        static List<int[]> GetAllPermutation(int[] array)
        {
            var size = array.Length;
            var res = new List<int[]>();
            do
            {
                var copy = new int[size];
                array.CopyTo(copy, 0);
                res.Add(copy);
            } while (NextPermutation(array));

            return res;
        }
    }
}


public static class Extentions
{
    public static int Int(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static long Long(this object obj)
    {
        return long.Parse(obj.ToString());
    }

    public static decimal Decimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double Double(this object obj)
    {
        return double.Parse(obj.ToString());
    }

    public static T2 GetValueZero<T1, T2>(this Dictionary<T1, T2> d, T1 key) where T2 : struct
    {
        T2 value;
        if (d.TryGetValue(key, out value))
        {
            return value;
        }
        return new T2();
    }
}



Measured memory_bytes: 64420