I have participated in Codeforces round 930 div2 and i solved first problem during the contest at that time it was showing me pretest passed verdict , but after the system testing it was showing that even i was not attempted the question (one possiblity is that it may get fail in system testing so it is supposed to give a error but it is showing that even i was not attempted it) then next morning i submitted the same code that i have submitted during the contest and and it get accepted. Solution I submitted after contest : Link1 Solution I submitted during the contest : Link2