#include <iostream>
#include <cmath>
#include <algorithm>
#include <string>
#include <vector>

#define FOR(i_type, i, i_min, i_max) for(i_type i = (i_min); i < (i_max); ++i)
using namespace std;

typedef vector<vector<bool>> Grid;

bool test_trans(vector<vector<bool>> grid /*copy*/, long i, long j, size_t blacks) {
	// 黒いマスを消す
	FOR (long, ii, 0, grid.size() - i) {
		FOR(long, jj, j > 0 ? 0 : -j, grid[0].size() - (j > 0 ? j : 0)) {
			if (grid[ii][jj]) {
				auto const dest = grid.at(ii + i).at(jj + j);
				if (dest) {
					grid[ii+i][jj+j] = 0;
					blacks-=2;
				}
				else {
					return false;
				}
			}
		}
	}

	return blacks == 0;
}

int main(void) {
	int H, W;
	cin >> H >> W;

	// 入力データを読み込む
	Grid grid(H, vector<bool>(W, false));
	size_t blacks = 0;
	FOR (size_t, i, 0, H) {
		string line;
		cin >> line;
		FOR(size_t, j, 0, W) {
			if (line[j] == '#') {
				grid[i][j] = true;
				blacks++;
			}
		}
	}

	bool ok = false;
	if (blacks == 0 or blacks & 1) ok = false;
	else {
		// Test all possible translations
		FOR(size_t, i, 0, H) {
			FOR (long, j, -W + 1, W) {
				if ((i != 0 or j != 0) and /* 平行移動していないからスキップ */
					(ok |= test_trans(grid, i, j, blacks))) break;
			}
		}
	}

	cout << (ok ? "YES" : "NO") << endl;

	return 0;
}