# coding: utf-8
from collections import deque

H, W = map(int, input().split())
# board[H][W]
board = [list(input()) for __ in range(H)]

index_board = [[c == "#" for c in row] for row in board]


def solve(check_board):
    if has_no_sharp(check_board):
        return False

    for h in range(H):
        for w in range(W):
            if h == w == 0:
                continue
            if check_paint(h, w, check_board):
                return True


def has_no_sharp(check_board):
    for row in check_board:
        if any(row):
            return False
    return True


def check_paint(h, w, check_board):
    copy_board = [row[:] for row in check_board]

    for h_ano in range(H):
        for w_ano in range(W):
            if copy_board[h_ano][w_ano]:
                if h_ano + h >= H or w_ano + w >= W or not copy_board[h_ano + h][w_ano + w]:
                    return False
                else:
                    copy_board[h_ano + h][w_ano + w] = False
    return True


if solve(index_board):
    print("YES")
else:
    board_reverse = [list(reversed(row)) for row in index_board]
    if solve(board_reverse):
        print("YES")
    else:
        print("NO")