Question

how did Sergi come to remember that he had met the begger​

Answer 1

Explanation:

When Sergei sees the beggar, he remembers that he has met the beggar two days ago in Sadovya Street. He also remembers that he had called himself a student who had been exiled from the school. When Sergei noticed that the beggar was wearing different overshoes one high and the other low, it confirms his doubt.