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

bool check(vector<vector<char>> S, int H, int W, int x, int y) {
    bool ans = false;
    bool used[H][W] = {};
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            if (!used[i][j] && S[i][j] == '#') {
                if (!(i + x < H && 0 <= j + y && j + y < W)) return false;
                if (used[i + x][j + y]) return false;
                if (S[i + x][j + y] != '#') return false;
                used[i][j] = used[i + x][j + y] = true;
                ans = true;
            }
        }
    }
    return ans;
}

int main() {
    int H, W;
    cin >> H >> W;
    vector<vector<char>> S(H, vector<char>(W));
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            cin >> S[i][j];
        }
    }
    bool ans = false;
    for (int i = 0; i < H; i++) {
        for (int j = -W + 1; j < W; j++) {
            if (i == 0 && j == 0) continue;
            ans |= check(S, H, W, i, j);
        }
    }
    cout << (ans ? "YES" : "NO") << endl;
}