#include <atcoder/all>
#include <bits/stdc++.h>
using ll = long long;
using ull = unsigned long long;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
using namespace std;
using namespace atcoder;
using mint = modint998244353;
const int inf = 1000000007;
const ll longinf = 1ll << 60;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int h, w;
    cin >> h >> w;
    vector<string> s(h);
    rep(i, h) cin >> s[i];
    // rep(i, h) s[i] = string(w, '#');
    vector<vector<int>> ok(h, vector<int>(w, 0));
    rep(i, h) rep(j, w) {
        ok[i][j] = s[i][j] == '.';
    }
    rep(i, h) rep(j, w) {
        if(s[i][j] == '.')
            continue;
        int u = i - 1, d = i + 1, l = j - 1, r = j + 1;
        while(1) {
            if(u < 0 || d >= h || l < 0 || r >= w)
                break;
            if(s[u][l] == '.' || s[u][r] == '.' || s[d][l] == '.' || s[d][r] == '.') {
                break;
            }
            ok[u][l] = ok[u][r] = ok[d][l] = ok[d][r] = 1;
            --u;
            ++d;
            --l;
            ++r;
        }
        if(d - u > 2) {
            ok[i][j] = 1;
        }
    }
    rep(i, h) rep(j, w) {
        if(!ok[i][j]) {
            cout << "No" << endl;
            return 0;
        }
    }
    cout << "Yes" << endl;
    return 0;
}