#!/usr/bin/env pypy3
# -*- coding: utf-8 -*-

import array
import collections
import itertools


IS_RED = 1
IS_BLUE = 2


def solve(height, width, black_cells):
    num_black_cells = len(black_cells)
    if num_black_cells == 0:
        return False
    elif num_black_cells % 2 == 1:
        return False
    it_a = ((0, dc) for dc in range(1, width))
    it_b = itertools.product(range(1, height), range(-width + 1, width))
    for dr, dc in itertools.chain(it_a, it_b):
        counter = 0
        painted = collections.defaultdict(int)
        for r0, c0 in black_cells:
            if counter >= num_black_cells:
                return True
            (r, c) = (r0 + dr, c0 + dc)
            if r < 0 or r >= height or c < 0 or c >= width:
                if not painted[(r0, c0)]:
                    break
            elif (not painted[(r0, c0)]) and (not painted[(r, c)]):
                if (r, c) not in black_cells:
                    break
                painted[(r0, c0)] = IS_RED
                painted[(r, c)] = IS_BLUE
                counter += 2
        else:
            return True
    else:
        return False


def main():
    h, w = map(int, input().split())
    black_cells = []
    for r in range(h):
        for c, cell in enumerate(input()):
            if cell == "#":
                black_cells.append((r, c))
    black_cells.sort()
    if solve(h, w, black_cells):
        print("YES")
    else:
        print("NO")


if __name__ == '__main__':
    main()