h, w = [ int(v) for v in input().split() ]

field = []
paint_list = []


for i in range(h):
    s = input()
    for j in range(len(s)):
        if s[j] == "#":
            paint_list.append((i,j))
move_list = []

for i in range((h+1)//2):
    for j in range((w+1)//2):
        move_list.append((i,j))
move_list = move_list[1:]


def paint(inlist):
    global paint_list
    y, x = inlist[0], inlist[1]
    red_list = []
    blue_list = []
    result = 0
    for i in paint_list:
        if i not in blue_list:
            red_list.append(i)
            j = (i[0]+y,i[1]+x)
            if j in paint_list:
                blue_list.append(j)
            else:
                result = -1
                break
    return result
ans = "NO"
for i in move_list:
    if paint(i) == 0:
        ans = "YES"
        break
print(ans)