using System;
using System.Collections.Generic;

namespace lamp
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] ini_input = Console.ReadLine().Split();
            int H = int.Parse(ini_input[0]);
            int W = int.Parse(ini_input[1]);

            List<List<char>> field = new List<List<char>>();

            List<List<int>> counter = new List<List<int>>();

            for(int i = 0; i < H; i++) { 
                List<char> column = new List<char>();
                List<int> columnCount = new List<int>();

                string sec_input = Console.ReadLine();
                int first_Lightning = -1;
                int light_counter = 0;

                for(int j = 0; j < W; j++){
                    // ' ' はchar型、" "はstring型
                    if(sec_input[j] == '.') {
                        light_counter++;
                        if(first_Lightning == -1) {
                            first_Lightning = j;
                        }
                        
                        if(j == (W - 1)) {
                            for(int k = j; k >= first_Lightning; k--) {
                                columnCount.Add(light_counter);
                            }
                        }
                    }
                    else if(sec_input[j] == '#') {
                        if(first_Lightning != -1) {
                            for(int k = j - 1; k >= first_Lightning; k--) {
                                columnCount.Add(light_counter);
                            }
                        }
                        light_counter = 0;
                        first_Lightning = -1;
                        columnCount.Add(0);
                    }
                  
                }
                counter.Add(columnCount);
            }

            int max = 0;

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

                int first_Lightning = -1;
                int light_counter = -1;
                
                for(int j = 0; j < H; j++) {
                
                    if(counter[j][i] > 0) {
                
                        light_counter++;
                
                        if(first_Lightning == -1) {
                            first_Lightning = j;
                        }

                        if(j == H - 1) {
                            for(int k = j; k >= first_Lightning; k--) {
                                int onLight = counter[k][i] + light_counter;

                                if(onLight > max) {
                                    max = onLight;
                                }
                            }
                        }
                
                    } else {
                
                        if (first_Lightning != -1) {
                
                            for(int k = j - 1; k >= first_Lightning; k--) {
                                int onLight = counter[k][i] + light_counter;
                                
                                if(onLight > max) {
                                    max = onLight;
                                }

                            }
                
                        }
                
                        light_counter = -1;
                        first_Lightning = -1;
                
                    }
                }
            }

            Console.WriteLine(max);
        }
    }
}

Measured memory_bytes: 41400