#include <bits/stdc++.h>
using namespace std;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define REP(i, n) FOR(i,0,n)
template <typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto &v : vec) is >> v; return is; }

int main()
{
    int H, W;
    cin >> H >> W;
    vector<string> S(H);
    cin >> S;
    REP(dx, H) for (int dy = -W + 1; dy < W; dy++) if (dx or dy)
    {
        auto T = S;
        bool f = true;
        REP(i, H) REP(j, W) if (T[i][j] == '#')
        {
            if (i + dx >= H or j + dy >= W or j + dy < 0 or T[i + dx][j + dy] == '.') f = false;
            else T[i + dx][j + dy] = '.';
        }
        if (f)
        {
            puts("YES");
            return 0;
        }
    }
    puts("NO");
}