Someproblemsarediffi的精選

問題詳情：Someproblemsaredifficulttosolve.Buttherearealotofnumberexpressionsthatcanhelp.Forexample,ifweputtwoandtwotogether,wemightcomeupwithrightanswer.Weknowthattwoheadsarebetterthanone,Itisalwaysbett...