#include <bits/stdc++.h>
#define SORT(a) sort(a.begin(), a.end())
#define RSORT(a) sort(a.rbegin(), a.rend())
#define REP(i, n) for (int i = 0; i < n; i++)
#define RREP(i, n) for (int i = n - 1; 0 <= i; i--)
#define FOR(i, start, end) for (int i = start; i < end; i++)
#define RFOR(i, start, end) for (int i = start - 1; 0 <= i; i--)
#define ALL(a) a.begin(), a.end()
using ll = long long;
using namespace std;
constexpr int INF32       = 1'050'000'000;
constexpr long long INF64 = 4'000'000'000'000'000'000;
constexpr int MOD7        = 1'000'000'007;
constexpr int MOD9        = 1'000'000'009;
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;
}
void print() { std::cout << '\n'; }
template <class H, class... T> void print(H &&head, T &&... args) {
    std::cout << head;
    sizeof...(args) == 0 ? std::cout << "" : std::cout << ' ';
    print(std::forward<T>(args)...);
}
template <class T> void print(std::vector<T> &v) {
    for (int i = 0; i < v.size(); i++) {
        std::cout << v[i];
        i == v.size() - 1 ? std::cout << '\n' : std::cout << ' ';
    }
}
template <class T> void print(std::vector<std::vector<T>> &v) {
    for (int i = 0; i < v.size(); i++) {
        for (int j = 0; j < v[i].size(); j++) {
            std::cout << v[i][j];
            j == v[i].size() - 1 ? std::cout << '\n' : std::cout << ' ';
        }
    }
}
void scan() {}
template <class H, class... T> void scan(H &&head, T &&... args) {
    std::cin >> head;
    scan(std::forward<T>(args)...);
}
template <class T> void scan(std::vector<T> &v) {
    for (auto &&i : v) {
        scan(i);
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int H, W;
    scan(H, W);
    vector<vector<char>> s(H, vector<char>(W));
    scan(s);
    vector<vector<int>> yoko(H, vector<int>(W));
    vector<vector<int>> tate(H, vector<int>(W));
    vector<vector<int>> sum(H, vector<int>(W, -1));

    REP(y, H) {
        int cnt = 0;
        REP(x, W) {
            if (s[y][x] == '.') {
                yoko[y][x] = ++cnt;
            } else {
                yoko[y][x] = -1;
                cnt        = 0;
            }
        }
    }
    REP(y, H) {
        int cnt = yoko[y][W - 1];
        RREP(x, W) {
            if (yoko[y][x] == -1) {
                cnt = -1;
                continue;
            }
            chmax(yoko[y][x], cnt);
            chmax(cnt, yoko[y][x]);
            sum[y][x] += cnt;
        }
    }

    REP(x, W) {
        int cnt = 0;
        REP(y, H) {
            if (s[y][x] == '.') {
                tate[y][x] = ++cnt;
            } else {
                tate[y][x] = -1;
                cnt        = 0;
            }
        }
    }
    REP(x, W) {
        int cnt = tate[H - 1][x];
        RREP(y, H) {
            if (tate[y][x] == -1) {
                cnt = -1;
                continue;
            }
            chmax(tate[y][x], cnt);
            chmax(cnt, tate[y][x]);
            sum[y][x] += cnt;
        }
    }
    int ans = 0;
    for (auto &&i : sum) {
        for (auto &&j : i) {
            chmax(ans, j);
        }
    }
    // print(sum);
    print(ans);

    return 0;
}

Measured memory_bytes: 51328