Imagine there's a big cube consisting of n^3 small cubes. Calculate, how many small cubes are not visible from outside.
For example, if we have a cube which has 4 cubes in a row, then the function should return 8, because there are 8 cubes inside our cube (2 cubes in each dimension)
import math
def not_visible_cubes(n):
    if (n < 2) : return 0
    else :
#         return long(math.pow(n-2,3))
        return (n-2)*(n-2)*(n-2)
    

import math
def not_visible_cubes(n):
    if (n < 2) : return 0
    else :
#         return long(math.pow(n-2,3))
        return (n-2)*(n-2)*(n-2)
    
