Codeforces Round #400 B.Sherlock and his girlfriend
题目Sherlockhasanewgirlfriend(sounlikehim!).Valentine’sdayiscomingandhewantstogifthersomejewelry.Heboughtnpiecesofjewelry.Thei-thpiecehaspriceequaltoi + 1,thatis,thepricesofthejewelryare2, 3, 4, …n + 1.