class MAP:
    __slots__ = ['li', 'len_li', 'b', 'ma', 'cnt']
    def  __init__(self, li):
        self.li = li
        self.len_li = len(li)
        self.b = [1] + [0] * (self.len_li - 1)
        self.ma = {a:i for i, a in enumerate(li)}
        self.cnt = 0
    def reset(self):
        self.b = [1] + [0] * (self.len_li - 1)
        self.cnt = 0
    def popleft(self):
        for i in range(self.cnt, self.len_li):
            if self.b[i] == 0:
                self.b[i] = 1
                for j in range(i + 1, self.len_li):
                    if self.b[j] == 0:
                        self.cnt = j
                        break
                return self.li[i]
        return (-100, -100)
    def find(self, a):
        if a not in self.ma:
            return False
        self.b[self.ma[a]] = 1
        return True
def f(m, y, x, len_m):
    for _ in range(len_m):
        a = m.popleft()
        ny = y + a[0]
        nx = x + a[1]
        if not m.find((ny, nx)):
            return False
    return True
def solve():
    h, w = map(int, input().split())
    s = tuple(input() for _ in range(h))
    c_cnt = sum(a.count('#') for a in s)
    if c_cnt == 0 or c_cnt & 1:
        return "NO"
    m = tuple((i, j) for i in range(h) for j in range(w) if s[i][j] == '#')
    dp = MAP(m)
    a = dp.li[0]
    c_cnt = (c_cnt - 2) // 2
    for i in range(1, len(m)):
        y = m[i][0] - a[0]
        x = m[i][1] - a[1]
        dp.b[i] = 1
        if f(dp, y, x, c_cnt):
            return "YES"
        dp.reset()
    return "NO"
print(solve())