Entry 2

Solved around 10-12 problems Difficulty level 2.Contest seem tough on glance.After seeing editorials, seems doable.I meant A,B problems.Seems I need more practise. I saw some of you guys mentioned math. I'm good at math for a average guy . What math concepts do i need to learn while also practising problem ? A prioritised list of math concepts would be better.I want to spend more time solving while also learning math.