#include <bits/stdc++.h>  // include all standard C++ libraries

using namespace std;

// Loops
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=int(a);i<int(b);++i)
#define _rrep(i,n) rrepi(i,n,0)
#define rrepi(i,a,b) for(int i=int(a)-1;i>=int(b);--i)

#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(xi, x) for (auto&& xi : x)
// Note: we can use rep(i,N) or rep(i,from,to)


// typedef
using ll = long long;
template <class T> using vec = vector<T>;
using vi   = vector<int>;
using vvi  = vector<vi>;
using vvvi = vector<vvi>;
using pii  = pair<int, int>;


// Constants

// Shorter repr for frequently used terms
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second


// Algorithms
#define all(x) (x).begin(), (x).end()
#define uniq(v) v.erase( unique(all(v)), v.end() )
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))

template<class T> pair<T, size_t> max(vector<T> &x){ auto it = max_element(all(x)); return mp(*it, it-x.begin()); }
template<class T> pair<T, size_t> min(vector<T> &x){ auto it = min_element(all(x)); return mp(*it, it-x.begin()); }

template<class T> inline bool chmax(T &maxval, const T &newval) { if (maxval<newval) { maxval=newval; return 1; } return 0; }
template<class T> inline bool chmin(T &minval, const T &newval) { if (minval>newval) { minval=newval; return 1; } return 0; }

// Utilities
// Grid world utilities
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
#define inside(H,W,y,x) 0<=(x) && (x)<(W) && 0<=(y) && (y)<(H)

inline int in() {int x; cin >> x; return x;} // read int from cin
inline  ll IN() {ll x; cin >> x; return x;}  // read ll from cin



// Debug
#ifdef LOCAL
  #include "dump.hpp"
  #define debug(x) cerr << #x << ": " << x << '\n'
#else
  #define dump(...)
  #define debug(x)
#endif

// Paste snippets here!!
int light_count_w(vector<string> &G, int i, int j){
  int cnt = 0;
  for(int k=j-1; k>=0; --k){
    if(G[i][k]=='#') break;
    cnt++;
  }
  for(int k=j+1; k<G[i].size(); ++k){
    if(G[i][k]=='#') break;
    cnt++;
  }
  return cnt;
}
int light_count_h(vector<string> &G, int i, int j){
  int cnt = 0;
  for(int k=i-1; k>=0; --k){
    if(G[k][j]=='#') break;
    cnt++;
  }
  for(int k=i+1; k<G.size(); ++k){
    if(G[k][j]=='#') break;
    cnt++;
  }
  return cnt;
}
// 

int main(){
  cin.tie(0); ios::sync_with_stdio(false);    // Magic for faster cin
  int H, W; cin >> H >> W;
  vector<string> G(H);
  rep(i,H) cin >> G[i];

  vvi Lh(H); rep(i,0,H) Lh[i].resize(W,0);
  vvi Lw(H); rep(i,0,H) Lw[i].resize(W,0);

  int m=0;
  rep(i,H){
    rep(j,W){
      //if(G[i][j]=='#') continue;
      //int h = light_count_h(G,i,j);
      //int w = light_count_w(G,i,j);
      //dump(i,j,h,w);
      //m = max(m,h+w+1);
      if(G[i][j]=='#'){
        Lh[i][j] = 0; Lw[i][j] = 0;
        continue;
      }
      if(i==0 || G[i-1][j]=='#'){
        Lh[i][j] = light_count_h(G,i,j);
      } else {
        Lh[i][j] = Lh[i-1][j];
      }
      if(j==0 || G[i][j-1]=='#'){
        Lw[i][j] = light_count_w(G,i,j);
      } else {
        Lw[i][j] = Lw[i][j-1];
      }
      m = max(m, Lh[i][j]+Lw[i][j]+1);
      //dump(i,j,Lh[i][j],Lw[i][j],G[i][j]);
    }
  }
  cout << m << endl;
  return 0;
}


Measured memory_bytes: 35968