#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 1000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	int h, w;
	char s[51][51];
	cin >> h >> w;
	int a = 0;
	REP(i, h) {
		REP(j, w) {
			cin >> s[i][j];
			if (s[i][j] == '#') {
				a++;
			}
		}
	}
	if (a % 2 == 1 || a == 0) {
		cout << "NO" << endl;
		return 0;
	}
	FOR(i, -h, h) {
		FOR(j, -w, w) {
			int cnt = 0;
			bool tb[51][51] = {};
			REP(k, h) {
				if (i == 0 && j == 0) break;
				REP(d, w) {
					if (s[k][d] == '#' && !tb[k][d]) {
						int d1 = k + i;
						int d2 = d + j;
						if (d1 < 0 || d2 < 0 || d1 >= h || d2 >= w) {
							break;
						}
						if (s[d1][d2] == '#' && !tb[d1][d2]) {
							tb[k][d] = true;
							tb[d1][d2] = true;
							cnt += 2;
						}
						else {
							break;
						}
					}
				}
			}
			if (a == cnt) {
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}