#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using pii = pair<int, int>;

char s[105][105];

int main() {
  int h, w;
  cin >> h >> w;
  rep(i, 105) rep(j, 105) s[i][j] = '.';
  rep(i, h) rep(j, w) cin >> s[i][j];

  rep(dy, h) rep(dx, w) {
    if (dy == 0 && dx == 0) continue;
    char c[105][105];
    rep(i, 105) rep(j, 105) c[i][j] = s[i][j];
    rep(y, h) rep(x, w) {
      if (c[y][x] == '#' && c[y + dy][x + dx] == '#') {
        c[y][x] = 'r';
        c[y + dy][x + dx] = 'b'; 
      }
    }
    bool ok = true;
    rep(y, h) rep(x, w) {
      if (c[y][x] == '#') ok = false;
      if (c[y][x] == 'r' && c[y + dy][x + dx] != 'b') ok = false;
      if (c[y][x] == 'b' && c[y + dy][x + dx] != '.') ok = false;
    }
    if (ok) {
      cout << "YES" << endl;
      return 0;
    }
  }

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