#include <iostream>
#include <map>
#include <set>
#include <algorithm>
#include <vector>
#include <sstream>
#include <string>
#include <functional>
#include <queue>
#include <deque>
#include <stack>
#include <limits>
#include <unordered_map>
#include <unordered_set>
#include <math.h>
#include <fstream>
#include <iterator>
#include <random>
#include <chrono>
 
 
#define forr(i,start,count) for (int i = (start); i < (start)+(count); ++i)
#define set_map_includes(set, elt) (set.find((elt)) != set.end())
#define readint(i) int i; cin >> i
#define readll(i) ll i; cin >> i
#define readdouble(i) double i; cin >> i
#define readstring(s) string s; cin >> s
 
typedef long long ll;
 
using namespace std;

ll modd = 1000*1000*1000+7;

ll binary_search(function<bool(ll)> func, ll start, ll end) {
    /*      func:int ->bool
            returns smallest int x where func(x) evaluates to true, searches in [start,end), it is assumed the values are false, .. , false, true ...
             */
    if (end <= start) {   return end;  }   // has to be here, otherwise func(end-1) in next line could be a problem
    if (!func(end-1)) {  return end;  }
    while (end-start>1) {
        ll mid = (start+end)/2;
        if (func(mid)) {  end = mid;  } else { start = mid;   }
    }
    if (func(start)) {  return start;  } else {  return end;   }
};


template<class T>
T fastpower(T a, long long n) {  // n must be >= 1
  if (n==0) {return 1;}
  if (n % 2 == 0) {  
      T halfpower = fastpower<T>(a, n/2);
      return (halfpower*halfpower) % modd;
  } else {
      if (n == 1) {  return a; } else {  
          T halfpower = fastpower<T>(a, n/2);
          return (((halfpower*halfpower)%modd)*a)%modd;
      }
  }
};


int main()   {

    ios_base::sync_with_stdio(false);

    cout.precision(17);
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    uniform_int_distribution<int> rand_gen(0, modd);   // rand_gen(rng) gets the rand no
 
//    auto start = chrono::steady_clock::now();
  
//    readint(test_cases);
    int test_cases = 1;
    forr(t, 1, test_cases) {
        readint(h); readint(w);
        vector<string> grid;
        grid.push_back(string(w+2, '#'));

        forr(i,0,h) {
            readstring(s);
            grid.push_back("#"+s+"#");
        }
        grid.push_back(string(w+2, '#'));

        vector<vector<int>> dist_to_left(h+2, vector<int>(w+2));
        forr(i,0,h+2) {
            int curr = 0;
            forr(j,0,w+2) {
                if (grid[i][j]=='#') {  curr = 0;  }
                else {  curr++; dist_to_left[i][j] = curr-1;   }
            }
        }
        vector<vector<int>> dist_to_right(h+2, vector<int>(w+2));
        forr(i,0,h+2) {
            int curr = 0;
            for(int j=w+1; j >= 0; --j) {
                if (grid[i][j]=='#') {  curr = 0;  }
                else {  curr++; dist_to_right[i][j] = curr-1;   }
            }
        }
        vector<vector<int>> dist_to_up(h+2, vector<int>(w+2));
        forr(j,0,w+2) {
            int curr = 0;
            forr(i,0,h+2) {
                if (grid[i][j]=='#') {  curr = 0;  }
                else {  curr++; dist_to_up[i][j] = curr-1;   }
            }
        }
        vector<vector<int>> dist_to_down(h+2, vector<int>(w+2));
        forr(j,0,w+2) {
            int curr = 0;
            for(int i=h+1; i >= 0; --i) {
                if (grid[i][j]=='#') {  curr = 0;  }
                else {  curr++; dist_to_down[i][j] = curr-1;   }
            }
        }


        int maxx = 0;
        forr(i,0,h+2) {
            forr(j,0,w+2) {
                if (grid[i][j]=='.') {
                    int right = dist_to_left[i][j], left = dist_to_right[i][j];
                    int up = dist_to_up[i][j], down = dist_to_down[i][j];
                    maxx = max(right+left+up+down+1, maxx);
                }
            }
        }

        cout << maxx << endl;


    }
 
//    auto end = chrono::steady_clock::now();
//    cout << chrono::duration_cast<chrono::milliseconds>(end - start).count() << endl;
 
    return 0;
}

Measured memory_bytes: 73968