#include"bits/stdc++.h"

using namespace std; 

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef long long LL;
typedef priority_queue<int> PQ_DESC;
typedef priority_queue<int, vector<int>, greater<int>> PQ_ASC;
typedef priority_queue<PII> PQ_DESC_PII;
typedef priority_queue<PII, vector<PII>, greater<PII>> PQ_ASC_PII;

#define ALL(c) (c).begin(),(c).end()
#define PB push_back
#define MP make_pair
#define SORT_ASC(c) sort(ALL(c))
#define SORT_DESC(c) sort(ALL(c), greater<typeof(*((c).begin()))>())
#define SIZE(a) int((a).size())

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define ROF(i,a,b) for(int i=(b-1);i>=(a);--i)
#define REP(i,n) FOR(i,0,n)
#define PER(i,n) ROF(i,0,n)

const double EPS = 1e-10;
const double PI  = acos(-1.0);
const int LARGE_INT = 1e9+100;
const int INF = 2e9+100;
const LL INF_LL = (LL)INF * 300 * 300;
const int MOD = 1e9+7;

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

LL modpow(LL a, LL n) {
    LL res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % MOD;
        a = a * a % MOD;
        n >>= 1;
    }
    return res;
}


void Main()
{
    int h,w;cin>>h>>w;

    vector<string> s(h);
    VVI left(h);
    VVI right(h);
    VVI up(h);
    VVI down(h);
    REP(i,h){
        left[i].resize(w);
        right[i].resize(w);
        up[i].resize(w);
        down[i].resize(w);
        cin>>s[i];
    }

    //left
    REP(i,h){
        REP(j,w){
            if(s[i][j] == '#'){
                left[i][j] = 0;
            }
            else{
                if(j == 0){
                    left[i][j] = 1;
                }
                else{
                    left[i][j] = left[i][j-1] + 1;
                }
            }
        }
    }
    //right
    REP(i,h){
        PER(j,w){
            if(s[i][j] == '#'){
                right[i][j] = 0;
            }
            else{
                if(j == w-1){
                    right[i][j] = 1;
                }
                else{
                    right[i][j] = right[i][j+1] + 1;
                }
            }
        }
    }
    //up
    REP(j,w){
        REP(i,h){
            if(s[i][j] == '#'){
                up[i][j] = 0;
            }
            else{
                if(i == 0){
                    up[i][j] = 1;
                }
                else{
                    up[i][j] = up[i-1][j] + 1;
                }
            }
        }
    }
    //down
    REP(j,w){
        PER(i,h){
            if(s[i][j] == '#'){
                down[i][j] = 0;
            }
            else{
                if(i == h-1){
                    down[i][j] = 1;
                }
                else{
                    down[i][j] = down[i+1][j] + 1;
                }
            }
        }
    }

    int result = 0;

    REP(i,h){
        REP(j,w){
            result = max(result,left[i][j]+right[i][j]+up[i][j]+down[i][j]-3);
        }
    }
    cout << result << endl;

    /*
    REP(i,h){
        REP(j,w){
            cerr << mp[i][j].first << " ";
        }
        cerr << endl;
    }
    cerr << endl;
    REP(i,h){
        REP(j,w){
            cerr << mp[i][j].second << " ";
        }
        cerr << endl;
    }
    */

	return;
}

int main()
{
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	cout << fixed << setprecision(15);
	Main();
    return 0;
}

Measured memory_bytes: 67328