/*Saurav Paul*/
#include<bits/stdc++.h>
#define endl '\n'
#define ll long long int
#define loop(i,a,b)           for(ll i=a;i<=b;++i)
#define boost		          ios_base::sync_with_stdio(0);
#define eb                    emplace_back
#define mp                    make_pair
#define clr(x)                x.clear()
#define MOD                   1e9+7
#define itoc(c)               ((char)(((int)'0')+c))
#define ctoi(c)               ((int)(((int)c)-'0'))
#define all(p)                p.begin(),p.end()
#define iscn(num)             scanf("%d",&num);
#define scn(num)              scanf("%lld",&num);
#define scn2(num,num2)        scanf("%lld%lld",&num,&num2);
using namespace std;
///////////////////////

#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef PAUL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define dbg(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
////////////////////////
/*
template<typename T>T set_bit(T N,T pos){return N=N | (1<<pos);}
template<typename T>T reset_bit(T N,T pos){return N= N & ~(1<<pos);}
template<typename T> bool check_bit(T N,T pos){return (bool)(N & (1<<pos));}
template<typename T>void bin_print(T N){bitset<25>bit(N);cerr<<bit.to_string()<<"\n";}
template<typename T> void max_self(T &a, T b){
	a=max(a,b);
}
template <typename T > void min_self(T &a, T b){
	a=min(a,b);
}
template <typename T > void add_self(T &a, T b){
	a+=b;
}
* */
////////////////////////

template<typename T> void ara_read(T &v,ll n){
	ll temp;
	for(ll i=0; i< n; i++){
		scanf("%lld",&temp);
		v.emplace_back(temp);
	}
}
template<typename T> void ara_print(T &v){
	for(ll x : v)
		printf("%lld ",x);
	puts("");
}
////////////////////////
const int INF = 1e9 + 99;
typedef pair<int,int> Pair;
typedef vector<int> vec;;
const int nax = 2000+5;
char s[nax][nax];
int dp[nax][nax];
int h , w;

int main()
{
	
	scanf("%d%d",&h,&w);
	for(int i =0 ; i < h ; i++)
		scanf("%s",s[i]);
	
	int maxi = 0;
	for (int i = 0 ; i < h ; i++){
		for(int j= 0 ; j < w ; j++){	
					/*			
					4 6
					#..#..
					.....#
					....#.
					#.#...
					*/		
				
			if(s[i][j]=='#')
				continue ;
			int cnt = 0,st= j;
			while(j < w){
				if(s[i][j]=='#')
					break;
				cnt++;
				j++;
			}
			for(st=st ; st < j ; st ++)
				dp[i][st] +=cnt ;
		}
	}

	for (int i = 0 ; i < w ; i++){
		for(int j= 0 ; j < h ; j++){	
					/*			
					4 6
					#..#..
					.....#
					....#.
					#.#...
					*/		
				
			if(s[j][i]=='#')
				continue ;
			int cnt = 0,st= j;
			while(j < h){
				if(s[j][i]=='#')
					break;
				cnt++;
				j++;
			}
			for(st=st ; st < j ; st ++)
				dp[st][i] +=cnt ;
		}
	}
	//~ puts("");
	for(int i = 0 ; i < h ; i++)
		for(int j = 0 ; j < w ; j++)
			maxi = max(maxi, (int)dp[i][j]);
			//~ printf("%d ",dp2[i][j]);
	
	printf("%d\n",maxi-1);
    return 0;
}


Measured memory_bytes: 19840