> 递推，
> F[P]表示第P层的不满意度，
> F[P]=∑(1<=I<P)(K[I]*((I-P)*a)+0.5*(I-P)(I-P-1))) + ∑(P<I<=M)(K[I]*((P-I)*b+0.5*(P-I)(P-I-1)))
> F[P+1]-F[P] = - ∑(1<=I<=M)K[I]*I + (b+P)∑(1<＝I<=P)K[I] - (a-P-1)∑(P+1<=I<=M)K[I]
> 
> 请教，谢过