In resampling in the next motion step, let's assume the following 3 particles are used
with the other ones are being ignored.
2 of them live in b2, 1 in c2, who again moves right,
and we get particles distributed as follows--2 fall into b3, 2 into b4, and 1 in c4.
So using the same measurement probability as before,
and now a measurement of a white square.
Tell me what the cumulative importance weight for the 3 new squares,
where 2 of the particles fall into b3, which happens to be a white square,
2 into b4, which happens to be a black square,
and 1 into c4, which happens to be a white square again.