#include <bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T> istream& operator >> (istream& is, vector<T>& vec) {
    for(T& x : vec) is >> x;
    return is;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int h, w;
    cin >> h >> w;
    vector<string> A(h);
    cin >> A;
    vector dp(h, vector(w, vector<int>(4, -1)));
    vector<int> Sp, Sm;
    auto rec = [&](auto rec, int y, int x, int ds) -> int {
        if(y < 0 || x < 0 || y >= h || x >= w) return 1;
        if(dp[y][x][ds] != -1) return dp[y][x][ds];
        if(A[y][x] == '.') return dp[y][x][ds] = 0;
        return dp[y][x][ds] = rec(rec, y + (ds & 1 ? 1 : -1), x + (ds & 2 ? 1 : -1), ds);
    };
    for(int y = 0; y < h; y++){
        for(int x = 0; x < w; x++){
            if(A[y][x] == '.') continue;
            bool flg = true;
            for(int s = 0; s < 4; s++){
                if(rec(rec, y, x, s) == 0){
                    flg = false;
                    break;
                }
            }
            if(flg){
                Sp.push_back(y + x);
                Sm.push_back(y - x);
            }
        }
    }
    sort(Sp.begin(), Sp.end());
    Sp.erase(unique(Sp.begin(), Sp.end()), Sp.end());
    sort(Sm.begin(), Sm.end());
    Sm.erase(unique(Sm.begin(), Sm.end()), Sm.end());
    for(int y = 0; y < h; y++){
        for(int x = 0; x < w; x++){
            if(A[y][x] == '.') continue;
            if(binary_search(Sp.begin(), Sp.end(), y + x) || binary_search(Sm.begin(), Sm.end(), y - x))continue;
            cout << "No\n";
            return 0;
        }
    }
    cout << "Yes\n";
}