摘要：
3126: [Usaco2013 Open]Photo Description Farmer John has decided to assemble a panoramic photo of a lineup of his N cows (1 <= N <= 200,000), which, as 阅读全文
摘要：
KPSUM - The Sum One of your friends wrote numbers 1, 2, 3, ..., N on the sheet of paper. After that he placed signs + and - between every pair of adja 阅读全文