#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<cmath>
#include<functional>
#include<map>
#include<cstdlib>
#include<complex>
#include<numeric>
#include<set>
#include<deque>
#include<queue>

using namespace std;
using Int = long long;
Int INF = 1LL << 60;
const Int MOD = 1000000000 + 7;

template<int Modulo = MOD> struct Mint {
	Int val;
	constexpr Mint(Int v = 0) noexcept : val(v% Modulo) {
		if (val < 0) v += Modulo;
	}
	constexpr int getmod() { return Modulo; }
	constexpr Mint operator - () const noexcept { return val ? Modulo - val : 0; }
	constexpr Mint operator + (const Mint& r) const noexcept { return Mint(*this) += r; }
	constexpr Mint operator - (const Mint& r) const noexcept { return Mint(*this) -= r; }
	constexpr Mint operator * (const Mint& r) const noexcept { return Mint(*this) *= r; }
	constexpr Mint operator / (const Mint& r) const noexcept { return Mint(*this) /= r; }
	constexpr Mint& operator += (const Mint& r) noexcept {
		val += r.val;
		if (val >= Modulo) val -= Modulo;
		return *this;
	}
	constexpr Mint& operator -= (const Mint& r) noexcept {
		val -= r.val;
		if (val < 0) val += Modulo;
		return *this;
	}
	constexpr Mint& operator *= (const Mint& r) noexcept {
		val = val * r.val % Modulo;
		return *this;
	}
	constexpr Mint& operator /= (const Mint& r) noexcept {
		Int a = r.val, b = Modulo, u = 1, v = 0;
		while (b) {
			Int t = a / b;
			a -= t * b; swap(a, b);
			u -= t * v; swap(u, v);
		}
		val = val * u % Modulo;
		if (val < 0) val += Modulo;
		return *this;
	}
	constexpr bool operator == (const Mint& r) const noexcept {
		return this->val == r.val;
	}
	constexpr bool operator != (const Mint& r) const noexcept {
		return this->val != r.val;
	}
	friend ostream& operator << (ostream& os, const Mint<Modulo>& x) noexcept {
		return os << x.val;
	}
	friend istream& operator >> (istream& is, Mint<Modulo>& x) noexcept {
		Int tmp; is >> tmp;
		x = Mint<Modulo>(tmp);
		return is;
	}
	friend constexpr Mint<Modulo> modpow(const Mint<Modulo>& a, Int n) noexcept {
		Mint res(1), tmp = a;
		while (n > 0) {
			if (n & 1) res *= tmp;
			tmp *= tmp;
			n >>= 1;
		}
		return res;
	}
};

using mint = Mint<>;

int main() {

	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	Int H, W;
	cin >> H >> W;

	vector<string> S(H);
	for (Int i = 0; i < H; i++) {
		cin >> S[i];
	}

	vector<vector<Int>> L(H, vector<Int>(W));//左
	vector<vector<Int>> R(H, vector<Int>(W));//右
	vector<vector<Int>> U(H, vector<Int>(W));//上 upper
	vector<vector<Int>> D(H, vector<Int>(W));//下 down

	//L
	for (Int i = 0; i < H; i++) {
		for (Int j = 0; j < W; j++) {
			if (j == 0) {
				if (S[i][j] == '#') {
					L[i][j] = 0;
				}
				else L[i][j] = 1;
			}

			else if (S[i][j] == '.') {
				L[i][j] = L[i][j - 1] + 1;
			}
			else {
				L[i][j] = 0;
			}
		}
	}

	//R
	for (Int i = 0; i < H; i++) {
		for (Int j = W-1; j >= 0; j--) {
			if (j == W-1) {
				if (S[i][j] == '#') {
					R[i][j] = 0;
				}
				else R[i][j] = 1;
			}

			else if (S[i][j] == '.') {
				R[i][j] = R[i][j + 1] + 1;
			}
			else {
				R[i][j] = 0;
			}
		}
	}

	//U
	for (Int j = 0; j < W; j++) {
		for (Int i = 0; i < H; i++) {
			if (i == 0) {
				if (S[i][j] == '#') {
					U[i][j] = 0;
				}
				else U[i][j] = 1;
			}

			else if (S[i][j] == '.') {
				U[i][j] = U[i-1][j] + 1;
			}
			else {
				U[i][j] = 0;
			}
		}
	}

	//D
	for (Int j = 0; j < W; j++) {
		for (Int i = H-1; i >= 0; i--) {
			if (i == H-1) {
				if (S[i][j] == '#') {
					D[i][j] = 0;
				}
				else D[i][j] = 1;
			}

			else if (S[i][j] == '.') {
				D[i][j] = D[i + 1][j] + 1;
			}
			else {
				D[i][j] = 0;
			}
		}
	}

	Int ans = 0;
	for (Int i = 0; i < H; i++) {
		for (Int j = 0; j < W; j++) {
			ans = max(ans, R[i][j] + L[i][j] + D[i][j] + U[i][j] - 3);
		}
	}
	cout << ans << "\n";

}

Measured memory_bytes: 129792