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]
for i in range(0,H):
    for j in range(0,W):
        for k in range(4):
            nx = i+dx[k]
            ny = i+dy[k] 
            if s[i][j] == "#":
                if 0 <= nx < W and 0 <= ny < H:
                   if s[nx][ny] == "#":
                    ans = "Yes"

print(ans)