row,column = map(int,input().split())
S = [list(input()) for i in range(row)]
status = "No"
coords = [[1,0],[-1,0],[0,1],[0,-1]]
for i in range(row):
  for j in range(column):
    if S[i][j] == "#":
      status = "No"
      for dx,dy in coords:
        if 0<= i+dy <row and 0<= j + dx < column:
          if S[i + dy][j + dx] ==  "#":
            status = "Yes"
print(status)