reimplement Bill's cofactor using getCofactor
reimplement Bill's cofactor using getCofactor

YetAnotherMinion/core,YetAnotherMinion/core,yangf4/core,yangf4/core,yangf4/core,YetAnotherMinion/core,yangf4/core,YetAnotherMinion/core,yangf4/core,YetAnotherMinion/core