isMarked
if (!isMarked(p)) {
if (!isMarked(blocks[i]))
if (!isMarked(blocks[j]))
if (p == 0 || isMarked(p))
if (p == 0 || isMarked(p))
if (p == 0 || isMarked(p))
if (p == 0 || isMarked(p))
if (isMarked(b))