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

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

    int H, W;
    cin >> H >> W;
    vector<string> S(H);
    rep(i, H) cin >> S[i];

    auto check = [&](vector<string> T, int di, int dj) {
        int cnt = 0;
        rep(i, H) rep(j, W) {
            if (T[i][j] == '#')
                cnt++;
        }
        if (cnt <= 1) return false;

        rep(i, H) rep(j, W) {
            if (T[i][j] == '.') continue;

            int ni = i + di, nj = j + dj;
            if (ni >= 0 && ni < H && nj >= 0 && nj < W) {
                if (T[ni][nj] == '#') {
                    T[i][j] = T[ni][nj] = '.';
                    continue;
                }
            }

            ni = i - di, nj = j - dj;
            if (ni >= 0 && ni < H && nj >= 0 && nj < W) {
                if (T[ni][nj] == '#') {
                    T[i][j] = T[ni][nj] = '.';
                    continue;
                }
            }
            return false;
        }
        return true;
    };

    for (int di = -H; di < H; ++di) {
        for (int dj = -W; dj < W; ++dj) {
            if (di == 0 && dj == 0) continue;

            if (check(S, di, dj)) {
                cout << "YES\n";
                return 0;
            }
        }
    }
    cout << "NO\n";

    return 0;
}