Question 18
Việt has 64 identical small cubes. In round 1, Việt builds a $4\times 4\times 4$ cube, paints its outside, then takes it apart. In round 2, Việt builds another $4\times 4\times 4$ cube from the same pieces, paints its outside, then takes it apart again. What is the greatest possible number of small cubes with exactly 3 painted faces after both rounds?
