def solve(h, w, map_ls):
    ct = map_ls.count('#')
    if ct == 0 or ct % 2 == 1:
        return 'NO'
    for dx in range(-(w - 1), w):
        for dy in range(h):
            if dx <= 0 and dy == 0:
                continue
            memo = [c for c in map_ls]
            for i_s, m in enumerate(memo):
                if m == '.':
                    continue
                sx, sy = i_s % w, i_s // w
                gx, gy = sx + dx, sy + dy
                i_g = w * gy + gx
                if not (0 <= gx < w and 0 <= gy < h):
                    break
                if not memo[i_g] == '#':
                    break
                memo[i_s] = '.'
                memo[i_g] = '.'
            else:
                if not '#' in memo:
                    return 'YES'
    return 'NO'

h, w = map(int, input().split())
map_ls = [c for i in range(h) for c in input()]

print(solve(h, w, map_ls))