hunterxhunter (Day 1, 2020, IATI) - https://arena.olimpiici.com/#/catalog/583/problem/101446
boycott - CHT, Aliens trick
braces (AB4, НОИ-3, 2018) - разделяй и владей оптимизация (https://arena.olimpiici.com/#/catalog/253/problem/100716)
