#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <queue>
#include <cmath>

using namespace std;
using ll = long long;
using ull = unsigned long long;


void ABC096C()
{
	int H, W;
	cin >> H >> W;
	vector<vector<int> > grid(H, vector<int>(W));
	for (int i = 0; i < H; ++i)
	{
		string str;
		cin >> str;
		for (int j = 0; j < W; ++j)
		{
			if (str[j] == '.')
				grid[i][j] = 0;
			else
				grid[i][j] = 1;
		}
	}
	vector<pair<int, int> > dx = { {0,1},{0,-1}, {1,0}, {-1,0} };
	for (int i = 0; i < H; ++i)
	{
		for (int j = 0; j < W; ++j)
		{
			if (grid[i][j] > 0)
			{
				bool found = false;
				for (int k = 0; k < 4; ++k)
				{
					int x = i + dx[k].first;
					int y = j + dx[k].second;
					if (x > -1 && x < H && y > -1 && y < W && grid[x][y] > 0)
					{
						found = true;
						break;
					}
				}
				if (!found)
				{
					cout << "No" << endl;
					return;
				}
			}
		}
		cout << "No" << endl;
		return;
	}
}#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <queue>
#include <cmath>

using namespace std;
using ll = long long;
using ull = unsigned long long;


void ABC096C()
{
	int H, W;
	cin >> H >> W;
	vector<vector<int> > grid(H, vector<int>(W));
	for (int i = 0; i < H; ++i)
	{
		string str;
		cin >> str;
		for (int j = 0; j < W; ++j)
		{
			if (str[j] == '.')
				grid[i][j] = 0;
			else
				grid[i][j] = 1;
		}
	}
	vector<pair<int, int> > dx = { {0,1},{0,-1}, {1,0}, {-1,0} };
	for (int i = 0; i < H; ++i)
	{
		for (int j = 0; j < W; ++j)
		{
			if (grid[i][j] > 0)
			{
				bool found = false;
				for (int k = 0; k < 4; ++k)
				{
					int x = i + dx[k].first;
					int y = j + dx[k].second;
					if (x > -1 && x < H && y > -1 && y < W && grid[x][y] > 0)
					{
						found = true;
						break;
					}
				}
				if (!found)
				{
					cout << "No" << endl;
					return;
				}
			}
		}
		cout << "No" << endl;
		return;
	}
}
int main()
{
	ABC096C();
	return 0;
}