// includes #include using namespace std; // macros #define pb emplace_back #define mk make_pair #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 all(x) (x).begin(),(x).end() #define sz(x) ((int)(x).size()) #define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end()) #define bit(n) (1LL<<(n)) // functions template bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;} template bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;} template istream &operator>>(istream &is, vector &vec){for(auto &v: vec)is >> v; return is;} template ostream &operator<<(ostream &os, const vector& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;} template ostream &operator<<(ostream &os, const set& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;} template ostream &operator<<(ostream &os, const unordered_set& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;} template ostream &operator<<(ostream &os, const multiset& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;} template ostream &operator<<(ostream &os, const unordered_multiset& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;} template ostream &operator<<(ostream &os, const pair &p){os << p.first << " " << p.second; return os;} template ostream &operator<<(ostream &os, const map &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;} template ostream &operator<<(ostream &os, const unordered_map &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;} // types using ll = long long int; using P = pair; // constants const int inf = 1e9; const ll linf = 1LL << 50; const double EPS = 1e-10; const int mod = 1000000007; const int dx[4] = {-1, 0, 1, 0}; const int dy[4] = {0, -1, 0, 1}; // io struct fast_io{ fast_io(){ios_base::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20);} } fast_io_; string s[101]; string t[101]; int h, w; void rotate(){ rep(i, w)t[i] = string(h, '#'); rep(i, h)rep(j, w){ t[w-j-1][i] = s[i][j]; } swap(s, t); swap(h, w); } int main(int argc, char const* argv[]) { cin >> h >> w; rep(i, h)cin >> s[i]; int xmax = -1, xmin = h + 1, ymax = -1, ymin = w + 1; int cnt = 0; rep(i, h)rep(j, w){ if(s[i][j] == '.'){ cnt++; xmax = max(xmax, i); xmin = min(xmin, i); ymax = max(ymax, j); ymin = min(ymin, j); } } int all = (xmax - xmin + 1) * 2 + (ymax - ymin + 1) * 2 - 4; bool ok = true; for(int i = xmin; i <= xmax; i++)if(s[i][ymin] == '#')ok = false; for(int i = xmin; i <= xmax; i++)if(s[i][ymax] == '#')ok = false; for(int i = ymin; i <= ymax; i++)if(s[xmax][i] == '#')ok = false; for(int i = ymin; i <= ymax; i++)if(s[xmin][i] == '#')ok = false; if(ok && all == cnt){ cout << "YES" << endl; return 0; } rep(i_, 4){ bool ok = true; for(int i = xmin; i <= xmax; i++)if(s[i][ymin] == '#')ok = false; for(int j = ymin; j <= ymax; j++)if(s[xmax][j] == '#')ok = false; int i = xmax; while(i > xmin){ if(s[i][ymax] == '#'){ i++; break; } i--; } if(i == xmin)i++; int j = ymax; while(j > ymin){ if(s[i][j] == '#'){ j++; break; } j--; } if(j == ymin)j++; for(int k = i; k >= xmin; k--)if(s[k][j] == '#')ok = false; for(int k = j; k >= ymin; k--)if(s[xmin][k] == '#')ok = false; int al = (xmax - xmin + 1) + (ymax - ymin) + xmax - i + ymax - j + i - xmin + j - ymin - 1; if(ok && al == cnt){ cout << "YES" << endl; return 0; } rotate(); } cout << "NO" << endl; return 0; }