Hello guys,Few days ago this question was asked in Codechef cookoff.I was able to understand greedy part of the editorial but could not convince myself with DP approach.

Things I did not understand, In the picking of Pairs,where are we checking the conditions in which pair's difference is strictly less than D.I could not see it anywhere.

So basically I want you to please explain it to me.The more detailed the more helpful(as I am dumb :P).Thank you have a nice day.

[](https://discuss.codechef.com/questions/72500/sumpair-editorial)