【BZOJ】4511: [Usaco2016 Jan]Subsequences Summing to Sevens 前缀和(特殊的技巧)
DescriptionFarmerJohn'sNcowsarestandinginarow,astheyhaveatendencytodofromtimetotime.EachcowislabeledwithadistinctintegerIDnumbersoFJcantellthemapart.FJwouldliketotakeaphotoofacontiguousgroupofcowsbut,