H,W=map(int,input().split())
s=[list(input()) for i in range(H)]
dx=[0,0,1,-1]
dy=[-1,1,0,0]
L=[0]
k=0
#s[i][j]
#i in range(H)
#j in range(W)
def dfs(x,y):
    s[x][y]="."
    L[k]+=1
    for p in range(4):
        nx=x+dx[p]
        ny=y+dy[p]
        if 0<=nx<H and 0<=ny<W:
            if s[nx][ny]=="#":
                dfs(nx,ny)
for i in range(H):
    for j in range(W):
        if s[i][j]=="#":
            dfs(i,j)
            k+=1
            L.append(0)
if min(L[:-1])==1:
    print("No")
else:
    print("Yes")
#print(L[:-1])
