def inside(x, y):
    return 0 <= x < H and 0 <= y < W

def move(h, w):
    c = [[-1] * W for i in range(H)]
    for i in range(H):
        for j in range(W):
            # まだ塗られていない黒マスが見つかったら
            if s[i][j] == '#' and c[i][j] == -1:
                # このマスを赤に塗る
                c[i][j] = 0
                # 対応する黒マスがなければやめる
                ni = i + h; nj = j + w
                if not inside(ni, nj):
                    return False
                if s[ni][nj] != '#':
                    return False
                # 対応するマスを青に
                c[ni][nj] = 1

    return True


H, W = map(int, input().split())
s = []
black = 0
for i in range(H):
    s.append(list(input()))
    black += s[i].count('#')

if black == 0 or black & 1:
    print("NO")
    exit()

for h in range(-H, H):
    for w in range(-W, W):
        if h == w == 0:
            continue
        if move(h, w):
            print("YES")
            exit()
print("NO")