It seems the hierarchy.txt file contains a cyclic relation, (A belongs to B, B belongs to A).
We have the following lines :
(line 35999) 472755 526754 ADM
(line 375211) 526754 472755
According to allCountries.txt, we have the following informations :
472755 is the "Volgogradskaya Oblast’"
526754 is the "Mikhaylovka Urban Okrug"
472755 being an oblast (an administrative division, see https://en.wikipedia.org/wiki/Oblast), I'm quite sure that 472755 contains 526754. But what about the second relation described line 375211 ?
Is it an error ? Or how should deal with such a cycle relation ?
Any help would be appreciated !