Problem:
A man just come to codeforces with basic knowledge of CP. After looking the contests and taking part in some of it,he decided to do a strange thing that is he will never solve a problem none but the DIV2-D.He decides that with all the 2/2.5/3 hours he will get in a live contest, he will use those time to solve his favourite problem DIV2-D.
But as his very early days in CP he does not know any DSA or anything. He become frightened and helpless that he might not be able to gain the capability to solve just his favourite problem DIV2-D.Now he ask for help?
What path he should follow now to fulfill his dream.Let help help him .But there is a condition you cannot say him practice more D.He need to know the learning and practicing roadmap for achiving his dream.
Statistically speaking, most people solve problem D after solving A, B, and C first. So it must be that solving problems A, B and C makes it easier to solve problem D.