#include <iostream>
#include <array>
#include <algorithm>
#include <map>
#include <vector>
#include <list>
#include <cmath>
#include <stack>
#include <queue>
#include <climits>
#include <string.h>
#include <cctype>
#include <set>

#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int, int>;
using namespace std;

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

// a と b の最大公約数を返す関数
long long GCD(long long a, long long b) {
	if (b == 0) return a;
	else return GCD(b, a % b);
}

long long gcd(long long a, long long b)
{
	if (a % b == 0)
	{
		return(b);
	}
	else
	{
		return(gcd(b, a % b));
	}
}

long long lcm(long long a, long long b)
{
	return a * b / gcd(a, b);
}

// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
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) {
		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];
	}
} comb(2000005);

mint g(int r, int c) {
	return comb(r + c + 2, r + 1) - 1;
}

bool comp(int i, int j) {
	return i > j;
}

bool compare_by_b(pair<int, int> a, pair<int, int> b) {
	return a.second < b.second;
}

// h, w
int tate[2000][2000];
int yoko[2000][2000];
bool rigi[2000][2000];

int main()
{
	int h, w;
	cin >> h >> w;
	for (int i = 0; i < h; i++)
	{
		string s;
		cin >> s;
		for (int j = 0; j < w; j++)
		{
			if (s[j] == '#')
			{
				rigi[i][j] = true;
			}
			else
			{
				rigi[i][j] = false;
			}
		}
	}

	for (int i = 0; i < h; i++)
	{
		int count = 1;
		for (int j = 0; j < w; j++)
		{
			if (!rigi[i][j])
			{
				yoko[i][j] = count;
				count++;
			}
			else
			{
				count = 1;
				yoko[i][j] = 0;
			}
		}
	}

	for (int i = 0; i < h; i++)
	{
		bool isMax = true;
		int maxValue = 0;
		for (int j = w - 1; j >= 0; j--)
		{
			if (!rigi[i][j])
			{
				if (isMax)
				{
					maxValue = yoko[i][j];
					isMax = false;
				}
				else
				{
					yoko[i][j] = maxValue;
				}
			}
			else
			{
				isMax = true;
			}
		}
	}

	for (int j = 0; j < w; j++)
	{
		int count = 1;
		for (int i = 0; i < h; i++)
		{
			if (!rigi[i][j])
			{
				tate[i][j] = count;
				count++;
			}
			else
			{
				count = 1;
				tate[i][j] = 0;
			}
		}
	}

	for (int j = 0; j < w; j++)
	{
		bool isMax = true;
		int maxValue = 0;
		for (int i = h - 1; i >= 0; i--)
		{
			if (!rigi[i][j])
			{
				if (isMax)
				{
					maxValue = tate[i][j];
					isMax = false;
				}
				else
				{
					tate[i][j] = maxValue;
				}
			}
			else
			{
				isMax = true;
			}
		}
	}

	int ans = 0;
	for (int i = 0; i < h; i++)
	{
		for (int j = 0; j < w; j++)
		{
			if (tate[i][j] + yoko[i][j] - 1 > ans)
			{
				ans = tate[i][j] + yoko[i][j] - 1;
			}
		}
	}
	cout << ans;
}



Measured memory_bytes: 66688