import copy


def check(dy, dx):
    T = copy.deepcopy(S)
    paint = False
    for y in range(H):
        for x in range(W):
            if T[y][x]:
                if 0 <= y + dy < H and 0 <= x + dx < W and T[y + dy][x + dx]:
                    T[y + dy][x + dx] = 0
                    paint = True
                else:
                    return 0
    return paint


H, W = map(int, input().split())
S = [[1 if x == "#" else 0 for x in input()] for _ in range(H)]

ok = False
for dy in range(H):
    for dx in range(W):
        if dy == dx == 0:
            continue
        ok |= check(dy, dx)

S = [*map(lambda x: x[::-1], S)]

for dy in range(H):
    for dx in range(W):
        if dy == dx == 0:
            continue
        ok |= check(dy, dx)

print("YES" if ok else "NO")