large cube, after the surface is completely painted red, is divided into several small cubes with a volume equal to 1. If among these small cubes, the number of small cubes with six sides that are not painted red accounts for the total number of small cubes (8/27), then what is the side length of the big cube.
一个大正方体，表面全涂上红色后，被分割成若干个体积都等于1的小正方体，如果在这些小正方体中，六个面都没有涂红色的小正方体的个数占全部小正方体个数的(8/27)，那么大正方体的边长是多少．
<result>6</result>