#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];

  int cnt = 0;
  rep(i, h) rep(j, w) if (s[i][j] == '#') cnt++;
  if (cnt < 2) {
    cout << "NO" << endl;
    return 0;
  }

  rep(r, 2) {
    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 (ok) {
        cout << "YES" << endl;
        return 0;
      }
    }

    char t[105][105];
    rep(i, h) rep(j, w) {
      t[j][h - i - 1] = s[i][j];
    }
    swap(t, s);
  }

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