import sys
import time

def main():
    H, W = map(int, input().split())

    cells_list = []
    while len(cells_list) < H:
        cells_list.append(list(input().strip()))
    
    cells_tuple = tuple(tuple(i) for i in cells_list)
    cells_list = None

    black_list = []
    for r in cells_tuple:
        black_list.append([i for i in range(len(r)) if r[i]=='#'])
    
    black_tuple = tuple(tuple(i) for i in black_list)
    black_list = None

    start_time = time.time()

    for y in range((-H)+1, H):
        for x in range((-W)+1, W):
            if try_paint(cells_tuple, black_tuple, H, W, y, x) == True:
                print('YES')
                #print(format(time.time() - start_time))
                exit(0)
    
    print('NO')
    #print(format(time.time() - start_time))


def try_paint(cells_tuple, black_tuple, H, W, vecY, vecX):

    _cells = list(list(i) for i in cells_tuple)
    _black_list = list(list(i) for i in black_tuple)

    flg = None

    rangeY = list(range(0,H))
    #rangeX = list(range(0,W))
    
    if vecY < 0:
        rangeY.reverse()

    # pos関数はインデックス指定だと時間がかかるという事で
    if vecX < 0:
        #rangeX.reverse()
        for i in _black_list:
            i.reverse()

    for y in rangeY:
        while len(_black_list[y]) != 0:

            x = _black_list[y].pop()

            # 赤色に塗る
            #_cells[y][x] = 'R'
        
            #Todo 青色に塗る判定
            trgY = y + vecY
            trgX = x + vecX
            if trgY in rangeY and trgX in _black_list[trgY]:
                #_cells[trgY][trgX] = 'B'
                _black_list[trgY].remove(trgX)
                if flg == None: flg = True
            else:
                # flg = False
                return False

    # if flg == True:  
    #     print('')
    #     print('vec = ' + str(vecY) + ', ' + str(vecX))
    #     for r in _cells:
    #         print(''.join(r))
    #     print(flg)
    #     input()

    return flg

if __name__ == "__main__":
    main()