H,W = map(int,input().split())
s = [input() for i in range(H)]
ans = "No"
dx = [1,0,-1,0]
dy = [0,1,0,-1]
flag = True
for i in range(H):
    for j in range(W):
        if s[i][j] == "#":
            flag = False
if flag:
    print("Yes")
    exit()
if W >= 2 or H >= 2:    
     for i in range(H):
        for j in range(W):
            for k in range(4):
                nx = i+dx[k]
                ny = j+dy[k] 
                if s[i][j] == "#":
                    if 0 <= nx < H and 0 <= ny < W:
                       if s[nx][ny] == "#":
                           ans = "Yes"

print(ans)