H,W = map(int,input().split())
S = [input() for _ in range(H)]

for dz in range(1,H*W):
    dx,dy = divmod(dz,W)
    checked = [[0 for j in range(W)] for i in range(H)]
    for sz in range(H*W):
        sx,sy = divmod(sz,W)
        if S[sx][sy] == '#' and not checked[sx][sy]:
            nx,ny = sx+dx,sy+dy
            if 0<=nx<H and 0<=ny<W and S[nx][ny] == '#':
                checked[nx][ny] = 1
            else:
                break
    else:
        print('YES')
        break
else:
    print('NO')