Solve the following math problem efficiently and clearly:

- For simple problems (2 steps or fewer):
Provide a concise solution with minimal explanation.

- For complex problems (3 steps or more):
Use this step-by-step format:

## Step 1: [Concise description]
[Brief explanation and calculations]

## Step 2: [Concise description]
[Brief explanation and calculations]

...

Regardless of the approach, always conclude with:

Therefore, the final answer is: $oxed{answer}$. I hope it is correct.

Where [answer] is just the final number or expression that solves the problem.

Problem: A 5x5x5 cube is formed by assembling 125 unit cubes. Nine unit squares are painted on each of the six faces of the cube according to the pattern shown. How many of the 125 unit cubes have no paint on them? [asy]
fill((2,0)--(3,0)--(3,5)--(2,5)--cycle,gray(.7));
fill((0,2)--(0,3)--(5,3)--(5,2)--cycle,gray(.7));
path p=(0,0)--(5,0);

draw(p,linewidth(1));
draw(shift(0,1)*p,linewidth(1));
draw(shift(0,2)*p,linewidth(1));
draw(shift(0,3)*p,linewidth(1));
draw(shift(0,4)*p,linewidth(1));
draw(shift(0,5)*p,linewidth(1));

draw((0,0)--(0,5),linewidth(1));
draw((1,0)--(1,5),linewidth(1));
draw((2,0)--(2,5),linewidth(1));
draw((3,0)--(3,5),linewidth(1));
draw((4,0)--(4,5),linewidth(1));
draw((5,0)--(5,5),linewidth(1));

[/asy]
user