H, W = map(int, input().split())
S = []
for i in range(H):
    S.append([c for c in input()])

black = sum(S[i].count("#") for i in range(H))

if black % 2 == 1 or black == 0:
    print("NO")
    exit()
for h in range(H):
    for w in range(-W + 1,W):
        if h == 0 and w <= 0:
            continue
        s = [row[:] for row in S]
        cnt = 0
        flg = False
        for i in range(H):
            for j in range(W):
                if s[i][j] == "#":
                    if 0 <= i + h <H and 0 <= j+w < W and s[i+h][j+w] == "#":
                        s[i][j] = "r"
                        s[i+h][j+w] = "b"
                        cnt += 2
                    else:
                        flg = True
            if flg:
                break
        if cnt == black:
            print("YES")
            exit()
print("NO")