#USACO07OPEN

P2891 [USACO07OPEN]吃饭Dining(最大流+拆点)

Cowsaresuchfinickyeaters.Eachcowhasapreferenceforcertainfoodsanddrinks,andshewillconsumenoothers.FarmerJohnhascookedfabulousmealsforhiscows,butheforgottocheckhi...