The Second Iranian Combinatorics Olympiad(ICO 2021) was held on 30th of July 2021. ICO2021 was in three levels of Elementary, Advanced and Free. It was offered in two versions of offline and online and in online version it offers the online standing for the first time around the world in a theoritical contest. 1600 participatns in the form of 800 teams from 27 countries around the world participated in this contest. You can find the booklet and the ranking of ICO2021 from the ICO official website.