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

#define int ll
using ll = long long;

const int MOD = 1e9 + 7;

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);

    int n, m;
    cin >> n >> m;
    vector<string> grid(n);
    for (auto &s : grid) cin >> s;

    int i0 = -1, j0 = -1;
    for (int i = 0; i0 == -1 && i < n; i++)
        for (int j = 0; i0 == -1 && j < m; j++)
            if (grid[i][j] == '#') {
                i0 = i; j0 = j;
            }

    if (i0 == -1) {
        cout << "NO" << endl;
        return 0;
    }

    int cnt = 0;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            if (grid[i][j] == '#') {
                cnt++;
            }

    for (int i1 = 0; i1 < n; i1++) {
        for (int j1 = 0; j1 < m; j1++) {
            if (grid[i1][j1] == '#' && !(i0 == i1 && j0 == j1)) {
                bool ok = true;

                set<pair<int, int>> v;
                for (int di = -n; di < n; di++) {
                    for (int dj = -m; dj < m; dj++) {
                        int aqui = 0;
                        if (0 <= i0 + di && i0 + di < n && 0 <= j0 + dj && j0 + dj < m) {
                            if (grid[i0 + di][j0 + dj] == '#') {
                                //v0.insert({i0 + di, j0 + dj});
                                aqui++;
                            }
                        }
                        if (0 <= i1 + di && i1 + di < n && 0 <= j1 + dj && j1 + dj < m) {
                            if (grid[i1 + di][j1 + dj] == '#') {
                                //v1.insert({i1 + di, j1 + dj});
                                aqui++;
                            }
                        }

                        if (aqui == 2 && !v.count({i0+ di, j0 + dj}) && !v.count({i1 + di, j1 + dj})) {
                            v.insert({i0 + di, j0 + dj});
                            v.insert({i1 + di, j1 + dj});
                        }

                    }
                }

                ok &= v.size() == cnt;

                //for (auto pos : v0) {
                //    ok &= !v1.count(pos);
                //}

                if (ok) {
                    cout << "YES" << endl;
                    return 0;
                }
            }
        }
    }

    cout << "NO" << endl;
}