#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <iomanip>
#include <limits>
#include <bitset>

using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef pair<ll, ll> PL;
#define int ll

const ll MOD = 1000000007;
const ll INF_LL = (ll)1000000007 * 1000000007;
const int INF_INT = (int)1000000007;
const double PI = 3.14159265358979323846;

const int dx[4] = { 1, 0, -1, 0 };
const int dy[4] = { 0, 1, 0, -1 };

#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
#define irep(itr, st) for (auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for (auto itr = (st).rbegin(); itr != (st).rend(); ++itr)

#define m0(x) memset((x), 0, sizeof((x)))
#define m1(x) memset((x), -1, sizeof((x)))

// xにはvectorなどのコンテナ
#define ALL(x) (x).begin(), (x).end()  // sortなどの引数を省略したい
#define RALL(x) (x).rbegin(), (x).rend()  // sortなどの引数を省略したい
#define SIZE(x) ((ll)(x).size())     // sizeをsize_tからllに直しておく
#define MAX(x) *max_element(ALL(x))  //最大値を求める
#define MIN(x) *min_element(ALL(x))  //最小値を求める
#define all(x) (x).begin(), (x).end()

//略記
#define pb emplace_back  // vectorヘの挿入
#define mp make_pair     // pairのコンストラクタ
#define F first          // pairの一つ目の要素
#define S second         // pairの二つ目の要素

#define BITCOUNT __builtin_popcount
#define BITCOUNT_LL(x) __builtin_popcountll(x)

#define perm(c)             \
  sort(all(c));             \
  for (bool c##p = 1; c##p; \
       c##p = next_permutation(all(c)))  //順列 123 132 213 231 312 321

#define BIT(n) (1LL << (n))

#ifdef DEBUG
#define PRINT(A) std::cout << (#A) << ": " << (A) << std::endl;
#else
#define PRINT(A)
#endif

//入力高速化
struct IoSetup {
    IoSetup() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} iosetup;

template <class T>
inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <class T>
inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}



signed main() {
    int H,W; cin >> H >> W;
    vector<string> S(H);
    for (int i = 0; i < H; i++) {
        cin >> S[i];
    }
    vector<vector<int>> val(H, vector<int>(W,0));

    int startPos = 0;
    int endPos = -1;
    int count = 0;
    for (int i = 0; i < H; i++) {
        count = 0;
        for (int j = 0; j < W; j++) {
            if (S[i][j] == '.' && j != W - 1) {
                count++;
                if (startPos == -1) startPos = j;
            }
            else {
                if (S[i][j] == '.') { count++;  val[i][W-1] = count; }
                if (startPos == -1)continue; 
                for (int k = startPos; k < j; k++) {
                    val[i][k] = count;
                }
                count = 0;
                startPos = -1;
            }
        }
    }
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            //cout << val[i][j] << " ";
        }
        //cout << endl;
    }
    count = 0;
    for (int i = 0; i < W; i++) {
        count = 0;
        for (int j = 0; j < H; j++) {
            if (S[j][i] == '.' && j!=H-1) {
                count++;
                if (startPos == -1) startPos = j;
            }
            else {
                if (S[j][i] == '.') { count++;  val[H - 1][i] += count; }
                if (startPos == -1)continue;
                for (int k = startPos; k < j; k++) {
                    val[k][i] += count;
                }
                count = 0;
                startPos = -1;
            }
        }
    }

    int ans = 0;
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            chmax(ans, val[i][j]);
            //cout << val[i][j] << " ";
        }
        //cout << endl;
    }

    cout << ans-1 << endl;
}


Measured memory_bytes: 35840