#include <bits/stdc++.h>

using namespace std;
#define rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i,n) for (int i = (int)(n-1); i >= 0; --i)
#define Rep(i,a,b) for (int i = a; i < b; ++i)
#define rRep(i,a,b) for (int i = a; i > b; --i)
#define fore(i,a) for(auto &i:a)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define Unique(v) v.erase(unique(v.begin(), v.end()), v.end());
#define Bit(x,i) (((x)>>(i))&1)
using ll = long long;
using vi = vector<int>;
using vll = vector<long long>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vs = vector<string>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
struct settings{settings(){ios_base::sync_with_stdio(0); cin.tie(0); cout<<fixed<<setprecision(15);};}settingss;
const double PI = acos(-1);
const int INF = 1001001001;
const ll LINF = 1001001001001001001LL;

int H, W;
int cnt_al = 0;
string S[55];

bool check(int x, int y) {
  vector<vector<char>> T(H, vector<char>(W, '.'));
  rep(i, H) rep(j, W) T[i][j] = S[i][j];
  int cnt = 0;
  rep(i, H) {
    rep(j, W) {
      if(i+x > H-1 || j+y < 0 || j+y > W-1) continue;
      if(T[i][j] == '#' && T[i+x][j+y] == '#') {
        cnt++;
        T[i][j] = '.';
        T[i+x][j+y] = '.';
      }
    }
  }
  bool ok = true;
  rep(i, H) {
    rep(j, W) {
      if(T[i][j] == '#') ok = false;
    }
  }
  return ok;
}

int main() {
  cin >> H >> W;
  rep(i, H) cin >> S[i];
  rep(i, H) rep(j, W) if(S[i][j] == '#') cnt_al++;
  if(cnt_al%2 == 1 || cnt_al == 0) {
    cout << "NO" << endl;
    return 0;
  }
  rep(i, H) {
    Rep(j, -W+1, W) {
      if(i == 0 && j == 0) continue;
      if(check(i, j)) {
        cout << "YES" << endl;
        return 0;
      }
    }
  }
  cout << "NO" << endl;
}