#include <bits/stdc++.h>
using namespace std;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
int H, W;
vector<string> field(55);
vector<vector<bool>> seen(55, vector<bool>(55, false));
int ans = 0;
void dfs(int h, int w) {
  seen[h][w] = true;
  for (int dir = 0; dir < 4; dir++) {
    int nh = h + dy[dir];
    int nw = w + dx[dir];
    if (nh < 0 || nh >= H || nw < 0 || nw >= W) {
      continue;
    }
    if (seen[nh][nw]) {
      continue;
    }
    if (field[nh][nw] == '#') {
      dfs(nh, nw);
    }
  }
}
int main() {
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    cin >> field[i];
  }
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (field[i][j] == '#' && !seen[i][j]) {
        dfs(i, j);
        ans++;
      }
    }
  }
  if (ans <= 1) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}
