#include <bits/stdc++.h>
using namespace std;
int memoh[2000][2000], memow[2000][2000];
signed main() {
  int h, w;
  cin >> h >> w;
  for (long long i = 0; i < h; i++) {
    for (long long j = 0; j < w; j++) {
      char c;
      cin >> c;
      if (i == 0 && c == '.') memow[i][j] = 1;
      if (j == 0 && c == '.') memoh[i][j] = 1;
      if (i != 0 && c == '.') memow[i][j] = memow[i - 1][j] + 1;
      if (j != 0 && c == '.') memoh[i][j] = memoh[i][j - 1] + 1;
    }
  }
  for (int i = h - 1; i >= 0; i--) {
    for (int j = w - 1; j >= 0; j--) {
      if (i != h - 1) {
        if (memow[i + 1][j] != 0 && memow[i][j] != 0) {
          memow[i][j] = memow[i + 1][j];
        }
      }
      if (j != w - 1) {
        if (memoh[i][j + 1] != 0 && memoh[i][j] != 0) {
          memoh[i][j] = memoh[i][j + 1];
        }
      }
    }
  }
  int ans = 0;
  for (long long i = 0; i < h; i++) {
    for (long long j = 0; j < w; j++) {
      if (memow[i][j] != 0 && memoh[i][j] != 0)
        ans = max(ans, memow[i][j] + memoh[i][j] - 1);
    }
  }
  cout << ans << endl;
}
