A(ch)B(yng)Ͻ ?sh)ڍƽY×1+ƽUMYָ(sh)÷2×UM×1%
ƽUMYָ(sh) ˵1UMY/ƽY……˵nUMY/n-1ƽY÷HUM
~B(yng)Ͻ ݕr~Ӌ惦~Ϣ÷g(yng)Ӌl(f)(sh)