In the Codeforces Round #727 (Div 2), someone had a rating change of -x and his rank was y. After the plagiarism check, his rank was y-k and had a rating change of -(x+c). Why this occured as rank decreased so either rating change should remain the same or should increase? And that -c is costing that someone person from becoming "Z". Please look into it MikeMirzayanov.
Here, x,y,k and c are all positive and Z is one among them {Pupil, Specialist, Expert, Candidate Master, Master}.