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

int main(void) {
    int H, W;
    cin >> H >> W;
    char board[H][W];
    for (int i = 0; i < H; i++) {
        cin >> board[i];
    }
    bool ans = false;
    for (int dh = -H; dh <= H && !ans; dh++) {
        for (int dw = -W; dw <= W; dw++) {
            if (dh == 0 && dw == 0) continue;
            bool flag = true;
            int cnt = 0;
            vector<vector<bool> > checked(H, vector<bool>(W, false));
            for (int h = 0; h < H && flag; h++) {
                for (int w = 0; w < W; w++) {
                    if (board[h][w] == '#' && !checked[h][w]) {
                        cnt++;
                        checked[h][w] = true;
                        int nh = h + dh;
                        int nw = w + dw;
                        if (nh < 0 || nh >= H || nw < 0 || nw >= W) {
                            flag = false;
                            break;
                        }
                        if (board[nh][nw] != '#' || checked[nh][nw]) {
                            flag = false;
                            break;
                        }
                        checked[nh][nw] = true;
                    }
                }
            }
            if (cnt == 0) flag = false;
            if (flag) {
                ans = true;
                break;
            }
        }
    }
    cout << (ans ? "YES" : "NO") << endl;
    return 0;
}