Supposing I started off with a particle, which I know exactly the state it is in, hence, it is in a pure state. And hence also, its entropy is zero. Now, suppose we throw the particle into the black hole and be sucked in, then, then the area of the black hole increases and hence, the entropy of the black hole also increases. But, how can this be possible? I started off with a zero von Neumann entropy and why should the entropy/area of the black hole increase?