#include<bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  vector<vector<int>> S(H);
  for(auto& v: S) {
    string s;
    cin >> s;
    for(auto c: s) v.emplace_back((c=='#') ? 0 : 1);
  }

  auto h = S, v = S;
  for(auto i=0; i<H; ++i) {
    for(auto j=1; j<W; ++j)   if(S[i][j]) h[i][j] += h[i][j-1];
    for(auto j=W-1; 0<j; --j) if(S[i][j]) h[i][j-1] = h[i][j];
  }
  for(auto j=0; j<W; ++j) {
    for(auto i=1; i<H; ++i)   if(S[i][j]) v[i][j] += v[i-1][j];
    for(auto i=H-1; 0<i; --i) if(S[i][j]) v[i-1][j] = v[i][j];
  }

  auto ans = 0;
  for(auto j=0; j<W; ++j) for(auto i=0; i<H; ++i) if(S[i][j]) ans = max(ans, v[i][j]+h[i][j]-1);
  cout << ans << endl;
}
