H,W=map(int,input().split())
MAP=[input().strip() for i in range(H)]

for i in range(H):
    for j in range(W):
        S=[[0]*W for i in range(H)]

        flag=0

        for k in range(H):
            if flag==1:
                break
            for l in range(W):
                if MAP[k][l]=="#" and S[k][l]==0:
                    S[k][l]=1
                    if k+i<H and j+l<W and MAP[k+i][j+l]=="#" and S[k+i][j+l]==0:
                        S[k+i][j+l]=2
                    else:
                        flag=1
                        break

        if flag==0:
            print("YES")
            exit()

print("NO")