#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);

    int H,W; cin >> H >> W;
    vector<string> S(H);
    rep(i,H) cin >> S[i];
    int cnt = 0;
    rep(i,H)rep(j,W) if(S[i][j] == '#') cnt++;
    if(cnt <= 1) { cout << "NO" << endl; return 0; }

    for(int dx = - H + 1; dx <= + H - 1; dx++)
    for(int dy = - W + 1; dy <= + W - 1; dy++)
    if(dx || dy) {
        vector<string> T = S;
        rep(x,H)rep(y,W) {
            if(T[x][y] == '#' && 0 <= x + dx && x + dx < H && 0 <= y + dy &&  y + dy < W && T[x + dx][y + dy] == '#') {
                T[x][y] = 'R';
                T[x + dx][y + dy] = 'B';
            }
        }
        int ng = 0;
        rep(x,H)rep(y,W) if(T[x][y] == '#') ng = 1;
        if(!ng) { cout << "YES" << endl; return 0; }
    }
    cout << "NO" << endl; return 0;
}