#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (ll i = 0; i < n; i++)
#define rrep(i, n) for (ll i = n - 1; i >= 0; i--)
#define Rep(i, r, n) for (ll i = r; i < n; i++)
#define RRep(i, r, n) for (ll i = n - 1; i <= r; i--)
#define debug(x) cout << #x << ' ' << '=' << ' ' << (x) << endl;
#define fs first
#define sc second
#define int long long
#define pb push_back
#define mp make_pair
const int dx[] = {0, -1, 0, 1};
const int dy[] = {1, 0, -1, 0};
const int MOD = (1000000007);
//const int MOD = (998244353);
//const int INF = (1 << 30)-1;
const int INF = (1LL << 60)-1;
const double EPS = (1 >> 30);

template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return 1;} return 0;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return 1;} return 0;}

using Graph = vector<vector<pair<int, int>>>;
using Ki = vector<vector<int>>;
using Vi = vector<int>;

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(10);
    //---------------------------------------------
    
    int h,w;
    cin>>h>>w;
    vector<string> s(h);
    rep(i, h) cin >> s[i];
    vector<vector<int>> ans(h,vector<int>(w));

    int left[h][w]={};
    rep(i,h){
        rep(j,w){
            if(j==0){
                if(s[i][j]=='#') left[i][j]=0;
                else left[i][j]=1;
            }
            else{
                if(s[i][j]=='#') left[i][j]=0;
                else left[i][j]=left[i][j-1]+1;
            }
        }
    }
    int right[h][w]={};
    rep(i,h){
        rrep(j,w){
            if(j==w-1){
                if(s[i][j]=='#') right[i][j]=0;
                else right[i][j]=1;
            }
            else{
                if(s[i][j]=='#') right[i][j]=0;
                else right[i][j]=right[i][j+1]+1;
            }
        }
    }
    /*
    rep(i,h){
        rep(j,w){
            ans[i][j]=left[i][j]+right[i][j]-1;
            cout<<ans[i][j]<<" ";
        }
        cout<<endl;
    }
    */
    int up[h][w]={};
    for(int j=0;j<w;j++){
        for(int i=0;i<h;i++){
            if(i==0){
                if(s[i][j]=='#') up[i][j]=0;
                else up[i][j]=1;
            }
            else{
                if(s[i][j]=='#') up[i][j]=0;
                else up[i][j]=up[i-1][j]+1;
            }
        }
    }
    int down[h][w]={};
    for(int j=0;j<w;j++){
        for(int i=h-1;i>=0;i--){
            if(i==h-1){
                if(s[i][j]=='#') down[i][j]=0;
                else down[i][j]=1;
            }
            else{
                if(s[i][j]=='#') down[i][j]=0;
                else down[i][j]=down[i+1][j]+1;
            }
        }
    }
    /*
    rep(i,h){
        rep(j,w){
            ans[i][j]=up[i][j]+down[i][j]-1;
            cout<<ans[i][j]<<" ";
        }
        cout<<endl;
    }
    */
    int ansa=1;
    rep(i,h){
        rep(j,w){
            if(s[i][j]=='#') continue;
            ans[i][j]=right[i][j]+left[i][j]+up[i][j]+down[i][j]-3;
            ansa=max(ans[i][j],ansa);
        }
    }
    cout<<ansa<<endl;
    
    
    
}

Measured memory_bytes: 160896