#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(void) {
  ll h, w;
  cin >> h >> w;
  bool s[h][w];
  for (ll j = 0; j < h; j++) {
    string ss;
    cin >> ss;
    for (ll i = 0; i < w; i++) {
      s[i][j] = (ss[i] == '#');
    }
  }
  ll ans = 0;
  ll i, j;
  ll i_left, i_right;
  ll j_up, j_down;
  for (i = 0; i < w; i++) {
    for (j = 0; j < h; j++) {
      if (s[i][j]) {
        continue;
      }
      for (i_left = i;; i_left--) {
        if (i_left - 1 < 0 || s[i_left - 1][j]) {
          break;
        }
      }
      for (i_right = i;; i_right++) {
        if (i_right + 1 >= w || s[i_right + 1][j]) {
          break;
        }
      }
      for (j_up = j;; j_up--) {
        if (j_up - 1 < 0 || s[i][j_up - 1]) {
          break;
        }
      }
      for (j_down = j;; j_down++) {
        if (j_down + 1 >= h || s[i][j_down + 1]) {
          break;
        }
      }
      ans = max(ans, i_right - i_left + j_down - j_up + 1);
    }
  }
  cout << ans << endl;
}
