h,w=map(int,input().split())
s=[["."]*(w+2)]
for i in range(h):
    s+=[["."]+list(input())+["."]]
s+=[["."]*(w+2)]
for j in range(1,h+1):
    for k in range(1,w+1):
        if s[j+1][k]=="." and s[j-1][k]=="." and s[j][k+1]=="." and s[j][k-1]==".":
            print("No")
            exit()
print("Yes")