import sys

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

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

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



def try_paint(cells, H, W, vecY, vecX):

    _cells = list(list(i) for i in cells)

    flg = None

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

    for y in rangeY:
        for x in rangeX:

            # 赤色に塗る判定
            if _cells[y][x] == '#':
                _cells[y][x] = 'R'
            
                #Todo 青色に塗る判定
                trgY = y + vecY
                trgX = x + vecX
                if trgY in range(0,H) and trgX in range(0,W):
                    if _cells[trgY][trgX] == '#':
                        _cells[trgY][trgX] = 'B'
                        if flg == None: flg = True
                    else:
                        # flg = False
                        return False
                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()