For the permutational symmetry described above, we choose 3 fragments with no more than 24 atoms each and with p 1 = 1, p 2 = 7, and p 3 = 13. The results of the procedure for choosing the best fragments are one fragment of 24, and two of 23 atoms. The first fragment has a permutational symmetry of {3, 3, 3 and 24, respectively, were chosen so as to include interactions between {H15, H16, H17} and {H42, H43, H44}. Without including these interactions, there would be no repulsion between these groups of atoms, which could result in spatial overlap between the two ends of the molecule. The three fragments are shown in the red boxes of Fig. .