import sys

# sys.setrecursionlimit(1000005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

from copy import deepcopy

h, w = LI()
ss = [[c == "#" for c in SI()] for _ in range(h)]

a = deepcopy(ss)
for i in range(h):
    for j in range(w):
        if i and j and a[i][j]: a[i][j] += a[i-1][j-1]

b = deepcopy(ss)
for i in range(h):
    for j in range(w):
        if i and j+1<w and b[i][j]: b[i][j] += b[i-1][j+1]

c = deepcopy(ss)
for i in range(h)[::-1]:
    for j in range(w):
        if i+1<h and j and c[i][j]: c[i][j] += c[i+1][j-1]

d = deepcopy(ss)
for i in range(h)[::-1]:
    for j in range(w):
        if i+1<h and j+1<w and d[i][j]: d[i][j] += d[i+1][j+1]

x=[[0]*(w+1) for _ in range(h+1)]
y=[[0]*(w+1) for _ in range(h+1)]
for i in range(h):
    for j in range(w):
        k=min(a[i][j],b[i][j],c[i][j],d[i][j])
        if k>1:
            k-=1
            x[i-k][j-k]+=1
            x[i+k+1][j+k+1]-=1
            y[i-k][j+k]+=1
            y[i+k+1][j-k-1]-=1
            # pDB(i,j,k)
            # p2D(x)
            # p2D(y)
for i in range(h):
    for j in range(w):
        x[i+1][j+1]+=x[i][j]
        y[i+1][j-1]+=y[i][j]

# p2D(x)
# p2D(y)

for i in range(h):
    for j in range(w):
        if ss[i][j]==0 and x[i][j]+y[i][j]>0:
            print("No")
            exit()
        if ss[i][j]>0 and x[i][j]+y[i][j]==0:
            print("No")
            exit()
print("Yes")