// {{{ Templates
#include <bits/stdc++.h>

#define show(x) cerr << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz:" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = (ll)1e9 + 7LL;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

// }}}

int N, M;
inline bool in(const int x, const int y)
{
    return 0 <= x and x < M and 0 <= y and y < N;
}

inline int left(const int prev)
{
    return (prev + 1) % 4;
}

inline int right(const int prev)
{
    return (prev + 3) % 4;
}

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

    constexpr int dir[5] = {1, 0, -1, 0, 1};

    cin >> N >> M;
    vector<vector<bool>> ok(N, vector<bool>(M, true));
    int ch = 0;
    for (int i = 0; i < N; i++) {
        string s;
        cin >> s;
        for (int j = 0; j < M; j++) {
            if (s[j] == '#') {
                ok[i][j] = false;
            } else {
                ch++;
            }
        }
    }

    // for (int i = 0; i < N; i++) {
    //     for (int j = 0; j < M; j++) {
    //         if (ok[i][j]) {
    //             int neighbor = 0;
    //             for (int d = 0; d < 4; d++) {
    //                 const int dx = dir[d];
    //                 const int dy = dir[d + 1];
    //                 const int newx = j + dx;
    //                 const int newy = i + dy;
    //                 if (in(newx, newy) and ok[newy][newx]) {
    //                     neighbor++;
    //                 }
    //             }
    //             if (neighbor != 2) {
    //                 cout << "NO" << endl;
    //                 return 0;
    //             }
    //         }
    //     }
    // }

    for (int y = 0; y < N; y++) {
        for (int x = 0; x < M; x++) {
            if (ok[y][x]) {
                for (int d = 0; d < 4; d++) {
                    const int dx = dir[d];
                    const int dy = dir[d + 1];
                    const int newx = x + dx;
                    const int newy = y + dy;
                    vector<vector<bool>> checked(N, vector<bool>(M, false));
                    bool used_right = false;
                    if (in(newx, newy) and ok[newy][newx]) {
                        int prevdir = d;
                        int posx = newx;
                        int posy = newy;
                        int cnt = 0;

                        while (true) {
                            checked[posy][posx] = true;
                            cnt++;
                            if (posx == x and posy == y) {
                                break;
                            }
                            int nextx = posx + dir[prevdir];
                            int nexty = posy + dir[prevdir + 1];
                            if (in(nextx, nexty) and ok[nexty][nextx] and (not checked[nexty][nextx])) {
                                posx = nextx;
                                posy = nexty;
                                continue;
                            }
                            nextx = posx + dir[left(prevdir)];
                            nexty = posy + dir[left(prevdir) + 1];
                            if (in(nextx, nexty) and ok[nexty][nextx] and (not checked[nexty][nextx])) {
                                prevdir = left(prevdir);
                                posx = nextx;
                                posy = nexty;
                                continue;
                            }
                            if (not used_right) {
                                nextx = posx + dir[right(prevdir)];
                                nexty = posy + dir[right(prevdir) + 1];
                                if (in(nextx, nexty) and ok[nexty][nextx] and (not checked[nexty][nextx])) {
                                    prevdir = right(prevdir);
                                    posx = nextx;
                                    posy = nexty;
                                    used_right = true;
                                    continue;
                                }
                            }
                            break;
                        }
                        if (cnt == ch) {
                            cout << "YES" << endl;
                            return 0;
                        }
                    }
                }
                cout << "NO" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}