import sys
input=lambda: sys.stdin.readline().rstrip()
h,w=map(int,input().split())
S=[input() for _ in range(h)]
chk=False
for i in range(h):
  for j in range(w):
    if i==0 and j==0:
      continue
    else:
      cur=True
      C=[[False]*w for _ in range(h)]
      for ii in range(h):
        for jj in range(w):
          if S[ii][jj]==".":
            continue
          else:
            if C[ii][jj]==False:
              if ii+i<h and jj+j<w and S[ii+i][jj+j]=="#":
                C[ii+i][jj+j]=True
              else:
                cur=False
      if cur:
        chk=True
if chk:
  print("YES")
else:
  print("NO")