#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VRSORT(v) sort(v.begin(), v.end(),greater<long long int>());
#define INF 999999999
#define MOD 1000000007
#define M_PI 3.14159265358979323846
#define ALL(X) (X).begin(),(X).end()

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0};
int dy[]={0, 1, 0, -1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }


int H,W;
vector<string> S;

void input(){
  fast_io();
  #ifdef __LOCAL
    fs::path p = __FILE__;
    fs::path input,output;
    input = output = p.parent_path();
    input += string("/input/") + string(p.stem()) + string(".txt");
    output += string("/output/") + string(p.stem()) + string(".txt");
    freopen(input.c_str(), "r", stdin);
    freopen(output.c_str(), "w", stdout);
  #endif
  cin >> H >> W;
  S = fetch_vec<string>(H);
}

bool isIn(int i, int j){
  return (0<=i and i<H and 0<=j and j<W);
}

bool isWall(int i, int j){
  return S[i][j]=='#';
}

int countLight(int i, int j){
  if(S[i][j]=='#') return 0;
  int x,y;
  int ans = 0;
  for (int k = 0; k < 4; k++)
  {
    x = i+dx[k];
    y = j+dy[k];
    while(isIn(x,y)&&!isWall(x,y)){
      ans++;
      x += dx[k];
      y += dy[k];
    }
  }
  return ans+1;
}

// O(H^2W^2)
int solve(){
  vector<vector<int>> CountRow(H,vector<int>(W,0));
  vector<vector<int>> CountColumn(H,vector<int>(W,0));
  int ans=0;
  // TLEは改善せず。 
  // vector<int> maxRow(H,0),maxColumn(W,0);
  for (int i = 0; i < H; i++)
  {
    CountRow[i][0] = !isWall(i,0);
    for (int j = 1; j < W; j++)
    {
      if(isWall(i,j)) CountRow[i][j]=0;
      else CountRow[i][j] = 1+CountRow[i][j-1];
    }
    for (int j = W-2; j >= 0; j--)
    {
      if(!isWall(i,j)) CountRow[i][j] = max(CountRow[i][j],CountRow[i][j+1]);
    }
  }

  for (int j = 0; j < W; j++)
  {
    CountColumn[0][j] = !isWall(0,j);
    for (int i = 1; i < H; i++)
    {
      if(isWall(i,j)) CountColumn[i][j]=0;
      else CountColumn[i][j] = 1+CountColumn[i-1][j];
    }
    for (int i = H-2; i >= 0; i--)
    {
      if(!isWall(i,j)) CountColumn[i][j] = max(CountColumn[i][j],CountColumn[i+1][j]);
    }
  }



  for (int i = 0; i < H; i++)
  {
    for (int j = 0; j < W; j++)
    {
      if(S[i][j]=='#') continue;
      // if(ans>=maxRow[i]+maxColumn[j]) continue;
      // countLight(i,j)
      ans = max(ans,CountRow[i][j]+CountColumn[i][j]-1);
      if(ans>=(H+W-1)) {cout << ans << endl; return 0;}
    }
  }
  cout << ans << endl;
  return 0;
}

int main()
{
  input();
  solve();
  return 0;
}


Measured memory_bytes: 35968