#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = 1; i < (n+1); ++i)
const double PI  =3.141592653589793238463;
using namespace std;
using ll = long long;
const ll INF = +10010010000;
typedef pair<ll,int> P;
const int mod = 1000000007;

struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;}
  mint operator+(const mint a) const { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= a;}
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod-2);}
  mint& operator/=(const mint a) { return *this *= a.inv();}
  mint operator/(const mint a) const { return mint(*this) /= a;}
};
istream& operator>>(istream& is, const mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}

struct combination {
  vector<mint> fact, ifact;
  combination(int n):fact(n+1),ifact(n+1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i-1]*i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i-1] = ifact[i]*i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n]*ifact[k]*ifact[n-k];
  }
};

vector<vector<int>> L,R,U,D(2005,vector<int>(2005,-1));
vector<vector<char>> B(2005,vector<char>(2005));

// void dfs(int i, int j, int si, int sj){
//     if(B[i][j]=='#'||D[i][j]!=-1||i<0||j<<0||i>=n||j>=n)return;
//     dfs(i+1,j,si+1,sj);
//     dfs(i-1,j,si+1,sj);
//     dfs(i,j+1,si,sj+1);
//     dfs(i,j-1,si,sj+1);
//     D[i][j] = 
// }

int main(){
    int h,w;
    cin >> h >> w;
    vector<string> s(h);
    L.resize(2005,vector<int>(2005,-1));
    R.resize(2005,vector<int>(2005,-1));
    U.resize(2005,vector<int>(2005,-1));
    D.resize(2005,vector<int>(2005,-1));
    rep(i,h){
        cin >> s[i];
    }
    rep(i,h){
        rep(j,w){
            if(s[i][j]=='#')L[i][j]=0;
            else if(j == 0)L[i][j] = 1;
            else L[i][j] = L[i][j-1]+1;
        }
    }
    rep(i,h){
        for(int j = w-1;j>=0;--j){
            if(s[i][j]=='#')R[i][j]=0;
            else if(j == w-1)R[i][j] = 1;
            else R[i][j] = R[i][j+1]+1;
        }
    }
    
    rep(j,w){
        rep(i,h){
            if(s[i][j]=='#')D[i][j]=0;
            else if(i==0)D[i][j]=1;
            else D[i][j] = D[i-1][j]+1;
        }
    }
    rep(j,w){
        for(int i = h-1;i>=0;--i){
            if(s[i][j]=='#')U[i][j]=0;
            else if(i==h-1)U[i][j]=1;
            else U[i][j] = U[i+1][j]+1;
        }
    }
    int ans = -1;
    rep(i,w){
        rep(j,h){
            ans = max(ans,U[j][i] + D[j][i] + L[j][i]+R[j][i]-3);
        }
    }
    cout << ans << endl;
    return 0;
}

Measured memory_bytes: 72320