H, W = map(int, input().split())
c = []
cnt = 0
for _ in range(H):
    s = list(input())
    cnt += s.count('#')
    c.append(s)
if cnt == 0 or cnt%2==1:
    print('NO')
    exit()

def solve(i, j):
    w1, w2 = [], []
    w1.append([0, H, 1])
    w2.append([0, W, 1])
    w1.append([H-1, -1, -1])
    w2.append([W-1, -1, -1])
    p, q = w1[i<0], w2[j<0]
    b = set()
    for x in range(p[0], p[1], p[2]):
        for y in range(q[0], q[1], q[2]):
            if x+i<0 or x+i>H-1 or y+j<0 or y+j>W-1:
                if (x, y) not in b and c[x][y]=='#':
                    return False
                else:
                    continue
            if (x, y) in b or c[x][y] == '.':
                continue
            b.add((x, y))
            if c[x+i][y+j]=='.':
                return False
            else:
                b.add((x+i, y+j))
    return True

for i in range(-H+1, H):
    for j in range(-W+1, W):
        if i == j == 0:
            continue
        if solve(i, j):
            print('YES')
            exit()
print('NO')