#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os, const map<T,U>& mp){ os << "{"; for(auto& p : mp){ os << p << ","; } os << "}"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
using ll = long long;
using ull = unsigned long long;
using pii = std::pair<int,int>;
using vi = std::vector<int>;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/

int main(){
    int h,w; cin >> h >> w;
    vector<string> s(h);
    rep(i,h) cin >> s[i];

    vvi x(h,vi(w,0)),y(h,vi(w,0));
    rep(i,h){
        int cnt = 0;
        rep(j,w){
            if(s[i][j]=='#'){
                cnt=0;
                x[i][j] = 0;
            }else{
                x[i][j] += cnt;
                cnt++;
            }
        }
        cnt = 0;
        rrep(j,w){
            if(s[i][j]=='#'){
                cnt = 0;
                x[i][j] = 0;
            }else{
                x[i][j] += cnt;
                cnt++;
            }
        }
    }

    /* rep(i,h){ */
    /*     rep(j,w){ */
    /*         cout << x[i][j] << " "; */
    /*     } */
    /*     cout << endl; */
    /* } */
    /* cout << endl; */

    rep(j,w){
        int cnt = 0;
        rep(i,h){
            if(s[i][j]=='#'){
                cnt=0;
                x[i][j] = 0;
            }else{
                x[i][j] += cnt;
                cnt++;
            }
        }
        cnt = 0;
        rrep(i,h){
            if(s[i][j]=='#'){
                cnt = 0;
                x[i][j] = 0;
            }else{
                x[i][j] += cnt;
                cnt++;
            }
        }
    }

    /* rep(i,h){ */
    /*     rep(j,w){ */
    /*         cout << x[i][j] << " "; */
    /*     } */
    /*     cout << endl; */
    /* } */

    int ans = 0;
    rep(i,h){
        rep(j,w){
            ans = max(ans, x[i][j]);
        }
    }
    cout << ans+1 << endl;
}


Measured memory_bytes: 42300