#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h" // define macro "/D__MAI"

using namespace std;
typedef long long int ll;

#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:v){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(auto cnt=0ll;(cnt)<(l);++(cnt))
#define rrepeat(cnt,l) for(auto cnt=(l)-1;0<=(cnt);--(cnt))
#define iterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);++(cnt))
#define MD 1000000007ll
#define PI 3.1415926535897932384626433832795
template<typename T1, typename T2> ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << "(" << p.first << ":" << p.second << ")"; return o; }
template<typename T> T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> T& minset(T& to, const T& val) { return to = min(to, val); }
void bye(string s, int code = 0) { cout << s << endl; exit(code); }
mt19937_64 randdev(8901016);
inline ll rand_range(ll l, ll h) {
    return uniform_int_distribution<ll>(l, h)(randdev);
}

#if defined(_WIN32) || defined(_WIN64)
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#elif defined(__GNUC__)
#else
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0; T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc && cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var * sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
        inline MaiScanner& operator>>(long long& var) { input_integer<long long>(var); return *this; }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
            return *this;
        }
        template<typename IT> void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; }
    };
    class MaiPrinter {
    public:
        template<typename T>
        void output_integer(T var) {
            if (var == 0) { putchar_unlocked('0'); return; }
            if (var < 0)
                putchar_unlocked('-'),
                var = -var;
            char stack[32]; int stack_p = 0;
            while (var)
                stack[stack_p++] = '0' + (var % 10),
                var /= 10;
            while (stack_p)
                putchar_unlocked(stack[--stack_p]);
        }
        inline MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; }
        inline MaiPrinter& operator<<(int var) { output_integer<int>(var); return *this; }
        inline MaiPrinter& operator<<(long long var) { output_integer<long long>(var); return *this; }
        inline MaiPrinter& operator<<(char* str_p) { while (*str_p) putchar_unlocked(*(str_p++)); return *this; }
        inline MaiPrinter& operator<<(const string& str) {
            const char* p = str.c_str();
            const char* l = p + str.size();
            while (p < l) putchar_unlocked(*p++);
            return *this;
        }
        template<typename IT> void join(IT begin, IT end, char sep = '\n') { for (auto it = begin; it != end; ++it) *this << *it << sep; }
    };
}
MaiScanner scanner;
MaiPrinter printer;


/*

class DGraphF {
public:
    typedef int cap_t;
    size_t n_;
    struct Arc {
        int from, to;
        // 残量
        cap_t left;
        // 容量
        cap_t cap;

        Arc(int from = 0, int to = 0, cap_t w = 1) :from(from), to(to), left(w), cap(w) {}
        inline bool operator<(const Arc& a) const { return (left != a.left) ? left < a.left : (left<a.left) | (cap<a.cap) | (from<a.from) | (to<a.to); }
        inline bool operator==(const Arc& a) const { return (from == a.from) && (to == a.to) && (left == a.left) && (cap == a.cap); }
    };
    vector<vector<int>> vertex_to;
    vector<vector<int>> vertex_from;
    vector<Arc> edges;

    DGraphF(int n = 1) :n_(n), vertex_to(n), vertex_from(n) { }

    void connect(int from, int to, cap_t left) {
        vertex_to[(size_t)from].push_back((int)edges.size()); // toto
        vertex_from[(size_t)to].push_back((int)edges.size()); // fromfrom
        edges.emplace_back(from, to, left);
    }
};



void dinic(DGraphF &graph, vector<DGraphF::cap_t>& result, int i_source, int i_sink) {
    assert(i_source != i_sink);

    result.resize(graph.n_);
    vector<int> dist(graph.n_);
    queue<int> q;
    vector<int> flag(graph.n_);

    static function<DGraphF::cap_t(int, int, DGraphF::cap_t)> _dfs = [&](int u, int i_sink, DGraphF::cap_t mini) {
        // DAG
        // TODO: 経路再利用
        if (i_sink == u) return mini;
        if (flag[u]) return (DGraphF::cap_t) - 1;
        flag[u] = true;

        DGraphF::cap_t sumw = 0;
        bool term = true;
        for (int e : graph.vertex_to[u]) {
            auto& edge = graph.edges[e];
            if (edge.left > 0 && dist[u]>dist[edge.to]) {
                DGraphF::cap_t w = (mini < 0) ? edge.left : min(edge.left, mini);

                w = _dfs(edge.to, i_sink, w);
                if (w == -1) continue;
                edge.left -= w;
                result[edge.to] += w;

                sumw += w;
                mini -= w;
                term = false;
                flag[u] = false; // TODO: 末尾では? 

                if (mini == 0) return sumw;
            }
        }
        for (int e : graph.vertex_from[u]) {
            auto& edge = graph.edges[e];
            if (edge.cap>edge.left && dist[u]>dist[edge.from]) {
                DGraphF::cap_t w = (mini < 0) ? (edge.cap - edge.left) : min(edge.cap - edge.left, mini);

                w = _dfs(edge.from, i_sink, w);
                if (w == -1) continue;
                edge.left += w;
                result[edge.to] -= w;

                sumw += w;
                mini -= w;
                term = false;
                flag[u] = false;
                if (mini == 0) return sumw;
            }
        }
        return term ? (DGraphF::cap_t)(-1) : sumw;
    };


    for (int distbegin = 0; ; distbegin += (int)graph.n_) {

        q.emplace(i_sink); // bfsはsinkからsourceへの距離を計算．
        dist[i_sink] = distbegin + 1;
        while (!q.empty()) {
            int v = q.front();
            q.pop();
            for (int ie : graph.vertex_from[v]) {
                const auto edge = graph.edges[ie];
                if (0 < edge.left && dist[edge.from] <= distbegin) {
                    dist[edge.from] = dist[v] + 1;
                    q.emplace(edge.from);
                }
            }
            for (int ie : graph.vertex_to[v]) {
                const auto edge = graph.edges[ie];
                if (edge.left < edge.cap && dist[edge.to] <= distbegin) {
                    dist[edge.to] = dist[v] + 1;
                    q.emplace(edge.to);
                }
            }
        }
        fill(flag.begin(), flag.end(), false);

        if (dist[i_source] <= distbegin)
            break;
        else
            result[i_source] += _dfs(i_source, i_sink, -1);
    }
}
*/


ll m, n, kei;

string field[88];

// d=0 : x-axis
bool isok(int y, int x, int d, int len) {
    repeat(i, len) {
        if (field[y + i*(d)][x+i*(d^1)] == '#') return false;
    }
    return true;
}

int main() {
    
    scanner >> n;
    scanner.in(field, field + n);

    int best = 0;

    // 縦にいっぱいつめこむ

    {
        int top, bot, left_stat, right_stat, cnt;
        top = bot = 0;
        left_stat = right_stat = 0;
        cnt = 0;
        
        repeat(x, n) {
            if (!isok(1, x, 1, n - 2)) continue;

            if (x == 0)
                left_stat = (field[0][x] == '.') | ((field[n - 1][x] == '.') << 1);
            else if (x == n-1)
                right_stat = (field[0][x] == '.') | ((field[n - 1][x] == '.') << 1);
            else {
                if (field[0][x] == '.') ++top;
                if (field[n - 1][x] == '.') ++bot;
            }
            cnt += (field[0][x] == '.') || (field[n - 1][x] == '.');
        }
        maxset(best, cnt);

        // 一番上に水平に置く
        if (isok(0, 1, 0, n - 2)) {
            if (field[0][0] == '.') {
                // 水平+左端下+下+右端
                maxset(best, 1 + ((left_stat&2)>>1) + bot + !!(right_stat));
            }
            if (field[0][n - 1] == '.') {
                // 水平+左端+下+右端下
                maxset(best, 1 + ((right_stat & 2) >> 1) + bot + !!(left_stat));
            }
        }

        // 一番下に水平に置く
        if (isok(n-1, 1, 0, n - 2)) {
            if (field[n - 1][0] == '.') {
                // 水平+左端上+上+右端
                maxset(best, 1 + ((left_stat & 1)) + top + !!(right_stat));
            }
            if (field[n - 1][n - 1] == '.') {
                // 水平+左端+上+右端上
                maxset(best, 1 + ((right_stat & 1)) + top + !!(left_stat));
            }
        }
    }

    // 横にいっぱいつめこむ
    {
        int left, right, top_stat, bot_stat, cnt;
        left = right = 0;
        top_stat = bot_stat = 0;
        cnt = 0;

        repeat(y, n) {
            if (!isok(y, 1, 0, n - 2)) continue;

            if (y == 0)
                top_stat = (field[y][0] == '.') | ((field[y][n-1] == '.') << 1);
            else if (y == n - 1)
                bot_stat = (field[y][0] == '.') | ((field[y][n-1] == '.') << 1);
            else {
                if (field[y][0] == '.') ++left;
                if (field[y][n-1] == '.') ++right;
            }
            cnt += (field[y][0] == '.') || (field[y][n - 1] == '.');
        }
        maxset(best, cnt);

        // 一番左端に垂直に置く
        if (isok(1, 0, 1, n - 2)) {
            if (field[0][0] == '.') {
                maxset(best, 1 + ((top_stat & 2) >> 1) + right + !!(bot_stat));
            }
            if (field[n-1][0] == '.') {
                maxset(best, 1 + ((bot_stat & 2) >> 1) + right + !!(top_stat));
            }
        }

        // 一番右に垂直に置く
        if (isok(1, n-1, 0, n - 2)) {
            if (field[n - 1][0] == '.') {
                maxset(best, 1 + ((top_stat & 1)) + left + !!(bot_stat));
            }
            if (field[n - 1][n - 1] == '.') {
                maxset(best, 1 + ((bot_stat & 1)) + left + !!(top_stat));
            }
        }
    }

    // special case
    {
        bool ok = true;
        repeat(i, n - 1) {
            ok &= (field[0][i] == '.');
            ok &= (field[i][n-1] == '.');
            ok &= (field[n-1][n-1-i] == '.');
            ok &= (field[n-1-i][0] == '.');
        }
        if (ok) maxset(best, 4);
    }

    cout << best << endl;

    return 0;
}