#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MOD 1000000007
#define INF (1LL << 25) // 33554432
#define PI 3.14159265359
#define EPS 1e-12
//#define int ll

signed main(void) {
  int h, w;
  string s[55], t[55];
  cin >> h >> w;
  REP(i, h) cin >> s[i];

  REP(i, h) REP(j, w) {
    REP(k, h) t[k] = s[k];
    bool flag = false;
    REP(k, h) {
      REP(l, w) {
        if (t[k][l] == '#') {
          t[k][l] = 'R';
          if (k + i < h && l + j < w && t[k + i][l + j] == '#') {
            t[k + i][l + j] = 'B';
          } else {
            flag = true;
          }
        }
        if(flag) break;
      }
      if(flag) break;
    }
    if(!flag) {
      bool a = true;
      REP(k, h) REP(l, w) {
        if(t[k][l] == '#') a = false;
      }
      if(a) {
        cout << "YES" << endl;
        //REP(i, h) cout << t[i] << endl;
        return 0;
      }
    }
  }

  cout << "NO" << endl;
  return 0;
}