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):
    for sign in range(2):
      if i==0 and j==0:
        continue
      else:
        cur=True
        ct=0
        C=[[False]*w for _ in range(h)]
        if sign==0:
          for ii in range(h):
            for jj in range(w):
              if S[ii][jj]==".":
                continue
              else:
                ct+=1
                if C[ii][jj]==False:
                  if 0<=ii+i<h and 0<=jj+j<w and S[ii+i][jj+j]=="#":
                    C[ii+i][jj+j]=True
                  else:
                    cur=False
        else:
          for ii in range(h)[::-1]:
            for jj in range(w):
              if S[ii][jj]==".":
                continue
              else:
                ct+=1
                if C[ii][jj]==False:
                  if 0<=ii-i<h and 0<=jj+j<w and S[ii-i][jj+j]=="#":
                    C[ii-i][jj+j]=True
                  else:
                    cur=False
        if cur and ct:
          chk=True
if chk:
  print("YES")
else:
  print("NO")