#include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <array>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>

using namespace std;
using ll = long long;
using ull = unsigned long long;

#ifndef __MACRO_H__
#define __MACRO_H__

#define all(collection)  (collection).begin(), (collection).end()		// begin to end
#define rep(i, begin, end) for (ll i = begin; i < end; i++)					// repeat
#define repr(i, begin, end) for (ll i = begin - 1; end <= i; i--)		// repeat reverse

std::chrono::system_clock::time_point  start;

void TimeStart(void)
{
	start = std::chrono::system_clock::now();
}

void TimeEnd(void)
{
	auto time = std::chrono::system_clock::now() - start;
	auto msec = std::chrono::duration_cast<std::chrono::milliseconds>(time).count();
	cerr << endl << msec << " msec " << endl;
}

#endif

struct SHARP
{
	ll start;
	ll end;
};

class ABC129D
{
public:
	ABC129D()
	{
		cin >> h >> w;

		h = h + 2;
		w = w + 2;
		s.resize(h);
		rep(i, 0, w)
			s[0] += "#";
		rep(i, 1, h - 1)
		{
			string in; cin >> in;
			s[i] += "#" + in + "#";
			in.clear();
		}
		rep(i, 0, w)
			s[h - 1] += "#";
	}
	void Run(void)
	{

		SHARP sharp;
		vector<SHARP> sharp_index_h;
		vector<vector<ll>> ans(h, vector<ll>(w));
		rep(i, 0, h)
		{
			rep(j, 0, w - 1)
			{
				if (s[i][j] == '#' && s[i][j + 1] == '.')
				{
					sharp.start = j;
					sharp_index_h.push_back(sharp);
				}
				if (s[i][j] == '.' && s[i][j + 1] == '#')
					sharp_index_h.back().end = j + 1;
			}
			for(const auto & e: sharp_index_h)
			{
				rep(j, e.start + 1, e.end)
					ans[i][j] += e.end - e.start - 1;
			}
			sharp_index_h.clear();
		}

		vector<SHARP> sharp_index_w;
		rep(j, 0, w)
		{
			rep(i, 0, h - 1)
			{
				if (s[i][j] == '#' && s[i + 1][j] == '.')
				{
					sharp.start = i;
					sharp_index_w.push_back(sharp);
				}
				if (s[i][j] == '.' && s[i + 1][j] == '#')
					sharp_index_w.back().end = i + 1;
			}
			for (const auto& e : sharp_index_w)
			{
				rep(i, e.start + 1, e.end)
					ans[i][j] += e.end - e.start - 1;
			}
			sharp_index_w.clear();
		}

		ll max_ans = 0;
		rep(i, 0, h)
		{
			rep(j, 0, w)
			{
				if (max_ans < ans[i][j])
					max_ans = ans[i][j];
			}
		}

		cout << max_ans - 1;
	}
private:
	ll h;
	ll w;
	vector<string> s;
};

int main(void)
{
	ABC129D abc129d;
	abc129d.Run();

	return 0;
}


Measured memory_bytes: 35712