#include <bits/stdc++.h>
#include <boost/multiprecision/cpp_int.hpp>
using namespace std;

//#define int long long
//using ll = boost::multiprecision::cpp_int;
using ll = long long;
//constexpr int INF = 1e9;//INT_MAX=1<<31-1=2147483647
constexpr ll INF = (ll)1e18;//1<<63-1=9223372036854775807
constexpr ll MOD = (ll)1e9 + 7;
constexpr double EPS = 1e-9;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
#ifdef LOCAL_ENV
	#define debug(var) std::cout<<#var" = "<<var<<std::endl
#else
	#define debug(var)
#endif
#define p(var) std::cout<<var<<std::endl
#define PI (acos(-1))
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define all(a) (a).begin(), (a).end()
#define pb push_back
inline bool isnatural(double a) { return a>=0 && ceil(a)==floor(a); }
template<typename T> inline T power(T x, T n){ return n ? power(x*x%MOD,n/2)*(n%2?x:1)%MOD : 1; }
template<typename T> inline T gcd(T a, T b) { return b ? gcd(b,a%b) : a; }
template<typename T> inline T lcm(T a, T b) { return a / gcd(a,  b) * b; }
template<typename T1, typename T2>inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2>inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
template<typename T1, typename T2> ostream& operator<<(ostream& s, const pair<T1, T2>& p) {return s << "(" << p.first << ", " << p.second << ")";}
template<typename T> ostream& operator<<(ostream& s, const vector<T>& v) {
	for (int i = 0, len = v.size(); i < len; ++i){
		s << v[i]; if (i < len - 1) s << "\t";
	}
	return s;
}
template<typename T> ostream& operator<<(ostream& s, const vector< vector<T> >& vv) {
	for (int i = 0, len = vv.size(); i < len; ++i){
		s << vv[i] << endl;
	}
	return s;
}
template<typename T1, typename T2> ostream& operator<<(ostream& s, const map<T1, T2>& m) {
	s << "{" << endl;
	for (typeof(m.begin()) itr = m.begin(); itr != m.end(); ++itr){
		s << "\t" << (*itr).first << " : " << (*itr).second << endl;
	}
	s << "}" << endl;
	return s;
}

/*-----8<-----8<-----*/

constexpr ll H_MAX = 2000;
constexpr ll W_MAX = 2000;

ll H, W;
vector<string> a;
void input() {
	scanf("%lld%lld", &H, &W);

	rep(i, H){string s;cin>>s;a.push_back(s);}
}

void solve() {
	vector<vector<ll>> b0 = vector<vector<ll>>(H, vector<ll>(W, 0));
	vector<vector<ll>> b1 = vector<vector<ll>>(H, vector<ll>(W, 0));

	rep(w,W){
		rep(h,H){
			if(a[h][w]=='#'){
				b0[h][w]=0;
				//b1[h][w]=0;
			}else{
				b0[h][w]=(h>0) ? b0[h-1][w]+1 : 1;
				//b0[h][w]=(w>0)? b0[h][w-1]+1 :1;
			}
		}
		ll t=0;
		for(ll h=H-1;h>=0;h--){
			if(b0[h][w]==0)t=0;
			else if(t==0)t=b0[h][w];

			b0[h][w]=t;
		}
	}

	

	rep(h,H){
		rep(w,W){
			if(a[h][w]=='#'){
				//b0[h][w]=0;
				b1[h][w]=0;
			}else{
				//b0[h][w]=(h>0) ? b0[h-1][w]+1 : 1;
				b1[h][w]=(w>0)? b1[h][w-1]+1 :1;
			}
		}
		ll t=0;
		for(ll w=W-1;w>=0;w--){
			if(b1[h][w]==0)t=0;
			else if(t==0)t=b1[h][w];

			b1[h][w]=t;
		}
	}
	debug(b1);
	///	
	ll maxval=0;
	rep(h,H){
		rep(w,W){
			ll t=b0[h][w]+b1[h][w];
			chmax(maxval,t);
		}
	}

	printf("%lld\n", maxval-1);
}

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


Measured memory_bytes: 67072