#include <stdio.h>

#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V>
void __print(const pair<T, V> &x) {
    cerr << '{';
    __print(x.first);
    cerr << ',';
    __print(x.second);
    cerr << '}';
}
template <typename T>
void __print(const T &x) {
    int f = 0;
    cerr << '{';
    for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
    cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
    __print(t);
    if (sizeof...(v)) cerr << ", ";
    _print(v...);
}
#ifdef LOCAL
#define debug(x...)               \
    cerr << "[" << #x << "] = ["; \
    _print(x)
#else
#define debug(x...)
#endif

#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, a, b) for (int i = (a); i < (b); i++)

typedef long long ll;

//方針: 縦に何個明るくなるか、横に何個明るくなるかを別々に計算して、それらを足す
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll H, W;
    cin >> H >> W;
    vector<string> S(H);
    REP(i, H) cin >> S[i];
    debug(H, W, S);

    vector<vector<ll>> left(H, vector<ll>(W));
    vector<vector<ll>> right(H, vector<ll>(W));

    vector<vector<ll>> up(H, vector<ll>(W));
    vector<vector<ll>> down(H, vector<ll>(W));

    // left
    REP(y, H) {
        FOR(x, 1, W) {
            if (S[y][x] == '#')
                left[y][x] = 0;
            else {
                if (S[y][x - 1] == '#') {
                    left[y][x] = left[y][x - 1];
                } else {
                    left[y][x] = left[y][x - 1] + 1;
                }
            }
        }
    }

    // right
    REP(y, H) {
        for (int x = W - 2; x >= 0; x--) {
            if (S[y][x] == '#')
                right[y][x] = 0;
            else {
                if (S[y][x + 1] == '#') {
                    right[y][x] = right[y][x + 1];
                } else {
                    right[y][x] = right[y][x + 1] + 1;
                }
            }
        }
    }

    // up
    FOR(y, 1, H) {
        REP(x, W) {
            if (S[y][x] == '#')
                up[y][x] = 0;
            else {
                if (S[y - 1][x] == '#') {
                    up[y][x] = up[y - 1][x];
                } else {
                    up[y][x] = up[y - 1][x] + 1;
                }
            }
        }
    }

    // right
    for (int y = H - 2; y >= 0; y--) {
        REP(x, W) {
            if (S[y][x] == '#')
                down[y][x] = 0;
            else {
                if (S[y + 1][x] == '#') {
                    down[y][x] = down[y + 1][x];
                } else {
                    down[y][x] = down[y + 1][x] + 1;
                }
            }
        }
    }

    ll ans = 0;
    REP(y, H) {
        REP(x, W) {
            ll sum = left[y][x] + right[y][x] + up[y][x] + down[y][x];
            if (sum > ans) {
                ans = sum;
            }
        }
    }
    cout << ans + 1 << endl;  //自分のいる位置のぶん1を加える

    return 0;
}


Measured memory_bytes: 129920