/**
 *    author  : 𝒌𝒚𝒐𝒎𝒖𝒌𝒚𝒐𝒎𝒖𝒑𝒖𝒓𝒊𝒏
 *    created : 2020-04-01 12:15:36
**/

#include <iostream>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <complex>
#include <numeric>
#include <bitset>
#include <cassert>
#include <cctype>
#include <iomanip>
#include <random>
#include <utility>
#include <chrono>

using namespace std;

using int64 = long long;

template<class T> using binary_heap = std::priority_queue<T, std::vector<T>, std::greater<T>>;
template<class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& vec) { os << '{'; size_t n = vec.size(); for (size_t i = 0; i < n; ++i) { os << vec[i]; if (i != n - 1) os << ','; } os << '}'; return os; }
template<class T, class U> std::ostream& operator<<(std::ostream& os, const std::pair<T, U>& p) { return os << '{' << p.first << " " << p.second << '}'; }
template<class T, class U> std::ostream& operator<<(std::ostream& os, const std::map<T, U>& mp) { os << '{'; for (auto it = mp.begin(); it != mp.end(); ++it) { os << '{' << it->first << ':' << it->second << '}'; if (it != --mp.end()) os << ','; } os << '}'; return os; }
template<class T> std::ostream& operator<<(std::ostream& os, const std::set<T>& st) { os << '{'; for (auto it = st.begin(); it != st.end(); ++it) { os << *it; if (it != --st.end()) os << ','; } os << '}'; return os; }
template<class T> std::istream& operator>>(std::istream& is, std::vector<T>& vec) { size_t n = vec.size(); for (size_t i = 0; i < n; ++i) is >> vec[i]; return is; }

#define all(_) begin(_), end(_)
#define rall(_) rbegin(_), rend(_)

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__)
#else
#define debug(...) 1728
#endif

void debug_out() { std::cerr << '\n'; }

template <class Head, class... Tail>
void debug_out(Head&& head, Tail&&... tail) {
  std::cerr << head;
  if (sizeof...(Tail) != 0) std::cerr << ", ";
  debug_out(std::forward<Tail>(tail)...);
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);

  int h, w; cin >> h >> w;
  vector<string> s(h); cin >> s;

  vector<vector<int>> dp_right(h, vector<int>(w, 0));
  vector<vector<int>> dp_left(h, vector<int>(w, 0));
  vector<vector<int>> dp_down(h, vector<int>(w, 0));
  vector<vector<int>> dp_up(h, vector<int>(w, 0));

  for (int i = 0; i < h; ++i) {
    int cur = 0;
    for (int j = 0; j < w; ++j) {
      if (s[i][j] == '.') {
        ++cur;
      } else {
        cur = 0;
      }
      dp_left[i][j] = cur;
    }
  }

  for (int i = 0; i < h; ++i) {
    int cur = 0;
    for (int j = w - 1; j >= 0; --j) {
      if (s[i][j] == '.') {
        ++cur;
      } else {
        cur = 0;
      }
      dp_right[i][j] = cur;
    }
  }

  for (int i = 0; i < w; ++i) {
    int cur = 0;
    for (int j = 0; j < h; ++j) {
      if (s[j][i] == '.') {
        ++cur;
      } else {
        cur = 0;
      }
      dp_up[j][i] = cur;
    }
  }

  for (int i = 0; i < w; ++i) {
    int cur = 0;
    for (int j = h - 1; j >= 0; --j) {
      if (s[j][i] == '.') {
        ++cur;
      } else {
        cur = 0;
      }
      dp_down[j][i] = cur;
    }
  }

  int ans = 0;

  for (int i = 0; i < h; ++i) {
    for (int j = 0; j < w; ++j) {
      if (s[i][j] != '#') {
        ans = max(ans, dp_down[i][j] + dp_left[i][j] + dp_right[i][j] + dp_up[i][j] - 3);
      }
    }
  }

  cout << ans << endl;

  return 0;
}

Measured memory_bytes: 67328