#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#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>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#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>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#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>
#endif

using namespace std;
typedef long long ll;
typedef pair<int,int> Pint;
typedef pair<ll, ll> P;
//typedef pair<int, pair<int, int>> P;
//typedef tuple<int,int,int> T;
ll INFL = 1000000000000000010;//10^18 = 2^60
int INF = 1000000000;//10^9
ll MOD  = 1000000007;
//vector<int> dy = {0,0,1,-1};
//vector<int> dx = {1,-1,0,0};

char mp[2010][2010];
pair<Pint, Pint> lr[2010][2010];

int main(void){
	int H,W;
	cin >> H >> W;
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			cin >> mp[i][j];
		}
	}
	for(int i = 0; i < 2010; i++){
		for(int j = 0; j < 2010; j++){
			lr[i][j].first.first = -1;
			lr[i][j].first.second = H;
			lr[i][j].second.first = -1;
			lr[i][j].second.second = W;
		}
	}
	int last = 0;
	for(int i = 0; i < H; i++){
		last = -1;
		for(int j = 0; j < W; j++){
			if(mp[i][j] == '#'){
				last = j;
			}else{
				lr[i][j].second.first = last;
			}
		}
	}

	for(int i = 0; i < H; i++){
		last = W;
		for(int j = W-1; j >= 0; j--){
			if(mp[i][j] == '#'){
				last = j;
			}else{
				lr[i][j].second.second = last;
			}
		}
	}

	for(int j = 0; j < W; j++){
		last = -1;
		for(int i = 0; i < H; i++){
			if(mp[i][j] == '#'){
				last = i;
			}else{
				lr[i][j].first.first = last;
			}
		}
	}

	for(int j = 0; j < W; j++){
		last = H;
		for(int i = H-1; i >= 0; i--){
			if(mp[i][j] == '#'){
				last = i;
			}else{
				lr[i][j].first.second = last;
			}
		}
	}
	int ans = 0;
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			if(mp[i][j] == '#') continue;
			ans = max(ans, (lr[i][j].second.second - lr[i][j].second.first-1) + (lr[i][j].first.second - lr[i][j].first.first-1)-1);
		}
	}
	cout << ans << endl;

}


Measured memory_bytes: 67328