H,W=map(int,input().split())
S=[input() for i in range(H)]
cnt0=[[0]*(H+W) for i in range(H)]
cnt1=[[0]*(H+W) for i in range(H)]
for i in range(H):
  for j in range(W):
    if S[i][j]=='#':
      cnt0[i][i-j]+=1
      cnt1[i][i+j]+=1
for i in range(1,H):
  for j in range(H+W):
    cnt0[i][j]+=cnt0[i-1][j]
    cnt1[i][j]+=cnt1[i-1][j]
result0=[[0]*(H+W) for i in range(H)]
result1=[[0]*(H+W) for i in range(H)]
p=[[0]*W for i in range(H)]
for i in range(1,H-1):
  for j in range(1,W-1):
    if S[i][j]=='.':
      continue
    l=0
    r=min(i,H-1-i,j,W-1-j)
    while True:
      m=(l+r+1)//2
      k1=cnt0[i+m][i-j]
      k2=cnt1[i+m][i+j]
      if i-m>0:
        k1-=cnt0[i-m-1][i-j]
        k2-=cnt1[i-m-1][i+j]
      if k1+k2==2*(2*m+1):
        l=m
      else:
        r=m-1
      if l==r:
        break
    if l>0:
      result0[i-l][i-j]+=1
      result1[i-l][i+j]+=1
      p[i][j]+=1
      if i+m+1<H:
        result0[i+l+1][i-j]-=1
        result1[i+l+1][i+j]-=1
for i in range(1,H):
  for j in range(H+W):
    result0[i][j]+=result0[i-1][j]
    result1[i][j]+=result1[i-1][j]
for i in range(H):
  for j in range(W):
    count=result0[i][i-j]+result1[i][i+j]-p[i][j]
    if S[i][j]=='#':
      if count==0:
        print('No')
        exit()
    else:
      if count>0:
        p=[0]
        print(p[1])
p=[0]
print('Yes')