// competitive-verifier: PROBLEM https://yukicoder.me/problems/no/0179
#include <iostream>
#include <string>
#include <vector>
int main(void) {
    int h, w;
    std::cin >> h >> w;
    std::vector<std::string> b(h);
    for (auto &s : b) std::cin >> s;
    bool ans = false;
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            if (i == 0 && j == 0)
                continue;
            bool f = true;
            std::vector dp(h, std::vector(w, -1));
            for (int x = 0; x < h; ++x) {
                for (int y = 0; y < w; ++y) {
                    if (b[x][y] == '#') {
                        if (dp[x][y] == 1)
                            continue;
                        if (i + x < h && j + y < w && b[i + x][j + y] == '#')
                            dp[i + x][j + y] = 1;
                        else
                            f = false;
                    }
                }
            }
            ans |= f;
        }
    }
    std::cout << (ans ? "YES\n" : "NO\n");
    return 0;
}